# Azelaic acid: full monograph (Azelaic Rx)
> Source page: https://azelaicrx.com/monograph

Status: FDA-approved drug
Disclosure: Azelaic acid is FDA-approved as prescription topical drugs (Finacea for rosacea; Azelex). Over-the-counter azelaic-acid serums are cosmetics, not FDA-approved drugs.
Updated: 2026-08-14

## Key facts
- Status: FDA-approved drug
- Skin penetration: 3 to 5% into stratum corneum; up to 10% in epidermis and dermis (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Half-life, topical: About 12 hours (absorption rate-limited) (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Half-life, oral: About 45 minutes (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Endogenous plasma range: 20 to 80 ng/mL, diet-dependent (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Plasma on 15% gel BID: 42 to 63.1 ng/mL, inside the vehicle-arm range (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=66178511-5c1a-4ecd-bc98-2ceb54e710ac)
- Foam steady state: By day 5; day 7 Cmax 51.8 +/- 18.5 ng/mL (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=9fabd24e-4c3b-49a0-aa5f-c8d75ae67572)
- Follicular delivery: Reaches in vitro antimicrobial concentrations in follicular casts (source: https://europepmc.org/article/MED/8217752)
- Elimination: Mainly unchanged in urine (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Class: Saturated C9 dicarboxylic acid (nonanedioic acid) (source: https://pubchem.ncbi.nlm.nih.gov/compound/2266)
- Molecular weight: 188.22 Da (C9H16O4), CAS 123-99-9 (source: https://pubchem.ncbi.nlm.nih.gov/compound/2266)
- Systemic absorption: About 4% of a topical dose (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Topical half-life: About 12 hours (45 minutes oral) (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Normal plasma level: 20 to 80 ng/mL from diet and endogenous synthesis (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75)
- Most common side effect: Burning, stinging or tingling: 29% with 15% gel (source: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=66178511-5c1a-4ecd-bc98-2ceb54e710ac)
- Rosacea evidence grade: High certainty (Cochrane 2015; GRADE 2019) (source: https://europepmc.org/article/MED/25919144)
- Study rows on this site: 29 (24 human, 5 in vitro) (source: https://europepmc.org/article/MED/12789172)
- Verified citations: 52 (100% peer-reviewed or government) (source: https://europepmc.org/article/MED/25919144)

## What is azelaic acid?
Azelaic acid is a nine-carbon dicarboxylic acid (nonanedioic acid, C9H16O4, molecular weight 188.22, CAS 123-99-9), a white crystalline solid that is poorly soluble in cold water  [49,38]. It is not an exotic molecule: it is a normal dietary constituent of whole grain cereals and animal products, the body can form it endogenously, and normal plasma levels run 20 to 80 ng/mL depending on diet  [40]. The yeast Malassezia, which lives on everyone's skin, produces it naturally  [30].
In dermatology it exists in three parallel worlds. It is an FDA-approved prescription drug at 15% (Finacea gel and foam, for rosacea) and 20% (Azelex cream, for acne)  [41,42]. It is a cosmetic ingredient in over-the-counter serums, commonly around 10%, which are not drugs and get no FDA review  [47]. And it is a social-media staple credited with everything from fungal acne treatment to DHT blocking, claims this monograph grades against what was actually studied.
The honest summary: at prescription strengths, azelaic acid is one of the best-evidenced topical drugs in dermatology, with high-certainty evidence in rosacea and solid comparative trials in acne and melasma  [6,7]. At the strength most people actually buy, the direct evidence is close to zero  [52]. This page keeps those two facts separate, which is the single most useful thing anyone can tell you about azelaic acid.

## Key facts
Sourced fact chips render here: chemistry, FDA status, absorption, half-life, tolerability and this site's own content counts. Every chip carries its claim id and resolves to the numbered references  [40,38].

## Regulatory status: prescription drug above 15%, cosmetic below it
Azelaic acid is FDA-approved as prescription topical drugs (Finacea for rosacea; Azelex). Over-the-counter azelaic-acid serums are cosmetics, not FDA-approved drugs.
The approved products: Finacea 15% gel (NDA 021470) and Finacea Foam 15% (NDA 207071) for inflammatory papules and pustules of mild to moderate rosacea, Azelex 20% cream (NDA 020428) for mild-to-moderate inflammatory acne vulgaris, and multiple approved generic 15% gels (ANDAs 204637, 208011, 208724, 210549)  [41,43,42,44]. All are prescription-only in the United States.
Below the prescription tier, the rules change completely. Cosmetic products and ingredients do not need FDA premarket approval, with the exception of color additives  [47]. A 10% azelaic acid serum is legally a cosmetic: nobody reviewed its safety, effectiveness or manufacturing before it went on sale. There is also no lawful over-the-counter DRUG route for azelaic acid: FDA's OTC acne monograph permits benzoyl peroxide, salicylic acid, sulfur and sulfur-resorcinol combinations, and azelaic acid is not on that list  [46]. Products in FDA's label database registering 10 to 14% azelaic acid acne creams under monograph codes are self-submitted listings, not approvals  [45].
Compounded azelaic acid formulations sold by pharmacies and telehealth services sit in a third category: compounded drugs are not FDA-approved, and FDA does not verify their safety, effectiveness or quality before marketing  [48].

## What azelaic acid is approved for
Rosacea: the 15% gel and foam are indicated for topical treatment of the inflammatory papules and pustules of mild to moderate rosacea  [38,39]. The label is specific about what that excludes: although some erythema reduction occurred in patients who had papules and pustules, efficacy for treating erythema in the absence of papules and pustules has not been evaluated  [38]. If your rosacea is redness and flushing without bumps, the approved evidence does not cover you.
Acne: Azelex 20% cream is indicated for topical treatment of mild-to-moderate inflammatory acne vulgaris  [40].
Everything else on this page, melasma and post-inflammatory hyperpigmentation included, is off-label or outside the drug system entirely. Off-label does not mean unstudied: the melasma trials below are real randomized comparisons. It means FDA never reviewed the use, so the claims on this page are graded by the studies themselves, not by an approval.

## The concentration gap: what is studied versus what is sold
Here is the fact the skincare market blurs. Of the 17 interventional human studies in our evidence table, 16 tested the prescription strengths of 15% or 20%  [1,16]. Exactly one tested the 10% strength the cosmetic market actually sells, and it deserves description: an 8-week, randomized, vehicle-controlled split-face study with 23 completers, testing a COMBINATION of 0.1% retinal plus 10% azelaic acid, measuring skin texture, surface irregularities, redness and pores by imaging  [37]. It reported real improvements on those cosmetic endpoints. It is not an acne trial, not a rosacea trial, not a melasma trial, and the azelaic acid contribution cannot be separated from the retinal.
We searched for randomized trials of 10% azelaic acid serums used alone for acne, rosacea or melasma and found none  [52]. That does not prove 10% serums do nothing; concentration-response is plausible and untested territory. It proves that when a serum brand cites azelaic acid's clinical evidence, it is citing trials of a prescription product at 1.5 to 2 times the concentration in a different vehicle. The evidence-borrowing goes one direction: from the pharmacy shelf down.
This is why the concentration column exists in our study table, and why the explorer tool on the dosing pillar lets you filter every study by the strength it actually used  [37].

## Mechanism: what is documented, graded by evidence level
Start with the regulator's candor: the rosacea gel label states the mechanisms by which azelaic acid interferes with rosacea are unknown, and the Azelex label calls its own in vitro data of unknown clinical significance  [38,40]. Everything below is mechanism evidence, not proof that a given mechanism drives the clinical results.
Antimicrobial (in vitro, plus human follicular data): azelaic acid is active against Cutibacterium (Propionibacterium) acnes and Staphylococcus epidermidis, plausibly by disrupting bacterial intracellular pH; kill is rapid in acid conditions and weak at neutral pH  [40,25,26]. In vivo, a single application of 20% cream produced follicular concentrations in the in vitro inhibitory range  [31], and acne patients on 20% cream showed 2,500-fold reductions in follicular Micrococcaceae and 44-fold reductions in Propionibacterium species  [10].
Anti-keratinizing (human biopsy): treated skin shows thinner stratum corneum, fewer and smaller keratohyalin granules, and reduced filaggrin, consistent with reduced microcomedo formation  [40].
Tyrosinase inhibition (in vitro): the origin story. Dicarboxylic acids isolated from Malassezia (Pityrosporum) cultures in 1978 competitively inhibit tyrosinase, the rate-limiting enzyme of melanin synthesis, which is why azelaic acid ended up in pigment disorders at all  [23].
Anti-inflammatory (in vitro): at 20 mM, a concentration the authors state is achievable after 15% topical gel, azelaic acid suppresses UVB-induced IL-1beta, IL-6 and TNF-alpha in human keratinocytes through PPARgamma activation  [27].
5 alpha-reductase inhibition (in vitro only): azelaic acid potently inhibits the enzyme in skin homogenates, complete at 3 mmol/l  [24]. The authors themselves wrote that clinical use depends on in vivo confirmation. Thirty-seven years later, that confirmation does not exist; see the hair-loss question in the FAQ.
No effect on sebum: measured sebum excretion rate did not change in acne patients, so azelaic acid is not an oil-control drug  [10].

## How the approved products are applied
All three products follow the same skeleton: wash with a very mild soap or soapless cleanser, pat dry, apply a thin layer twice daily (morning and evening), wash your hands afterward, and let it dry before cosmetics go on top  [38,40]. The gel and foam labels add: reassess the diagnosis if there is no improvement after 12 weeks  [38,39]. The foam is applied to the entire facial area (cheeks, chin, forehead and nose), shaken well first, using the smallest amount that covers with a thin layer  [39].
How much is a thin layer? Two published anchors exist. The foam label's pharmacokinetic study used a mean of 0.94 grams of foam (141 mg azelaic acid) per whole-face application  [39]. And dermatology's standard measure, the fingertip unit (about 0.5 g, the ribbon from a 5 mm nozzle along the last finger joint), allocates 2.5 FTU for face and neck, with one FTU covering about 286 square centimeters  [32,33]. For a face-only application of a 15% gel, that arithmetic lands close to the same 1 gram per application the foam study measured. The application-quantity tool on this site does that arithmetic against your tube size, with every constant cited.
What to avoid while using it, per the labels: alcoholic cleansers, tinctures and astringents, abrasives and peeling agents, and occlusive dressings  [38]. Keep it out of eyes and mucous membranes  [38]. The foam is flammable: no fire, flame or smoking during and right after application  [39].

## The evidence at a glance
Our graded table holds 29 rows: 24 human and 5 in vitro, each with species, design, n, concentration, dose, duration, outcome and effect size  [6,22]. The shape of the evidence differs by condition, and the differences are the story: rosacea has the regulator-grade base (two pivotal programs plus Cochrane-rated high-quality evidence), acne has a deep comparative record showing equivalence with standard topicals, melasma has genuine head-to-head wins and a mid-field rank in modern network meta-analysis, and the viral claims (fungal acne, DHT) have laboratory data and no trials.
Every number in this section resolves through the claims ledger to a fetched source, and the citation manifest ships with the page so the trail is machine-checkable  [6].

## Rosacea: the strongest case
The pivotal base: two identical vehicle-controlled phase III trials (664 subjects, 12 weeks) found mean inflammatory lesion reductions of 57.9% versus 39.9% and 50.0% versus 38.2%, with investigator global success in 61% versus 40% and 61% versus 48%  [38,1]. Erythema in patients with papules and pustules improved more than vehicle too (44% versus 29%, 46% versus 28%), with no serious treatment-related adverse events  [1]. The foam repeated the pattern in 1362 subjects: IGA success 32.1% versus 23.4% and 43.4% versus 32.5%  [39,4].
Against the standard comparator, 15% azelaic acid gel beat metronidazole 0.75% gel in a 251-patient randomized trial: 72.7% versus 55.8% lesion reduction, more erythema improvement, and continued gains after metronidazole plateaued at week 8  [2]. In a 40-patient split-face trial, 20% cream equaled metronidazole cream on lesions with better global-improvement ratings  [3]. The price of that efficacy is tolerability: 19.4% adverse reactions versus 7.1% with metronidazole in the active-controlled trial  [38].
The syntheses agree with unusual force. Cochrane 2015 (106 studies, 13,631 participants) rated azelaic acid's superiority over placebo as HIGH quality evidence, participant-assessed RR 1.46  [6]. The 2019 GRADE update (152 studies, 20,944 participants) kept azelaic acid and ivermectin as the two high-certainty topicals for papules and pustules  [7]. A 2025 network meta-analysis ranked azelaic acid 20% first for IGA improvement (OR 8.54) while flagging azelaic acid 15% as the only topical with a significant adverse-event odds ratio (1.95)  [8]. Best in class and most stinging in class, in the same dataset: that trade-off is the honest headline.
Scope limit, straight from the label: none of this covers erythema without papules and pustules  [38]. If your rosacea is flushing and background redness only, this drug's approved evidence does not speak to you.

## Acne: equivalence with the standards, minus the antibiotics
The 20% cream's controlled program: better than vehicle in moderate inflammatory acne (92 patients, 3 months), equal to tretinoin 0.05% in comedonal acne (289 patients, 6 months) with fewer local side effects  [9], and only just short of oral tetracycline over 6 months  [11]. A separate placebo-controlled program documented the mechanism in patients: inflamed lesions fell within a month, follicular bacteria fell up to 2,500-fold, and sebum did not change  [10].
The 15% gel matched both modern standards in two randomized blinded trials: median inflamed-lesion reductions of 70% versus benzoyl peroxide 5% (351 patients) and 71% versus clindamycin 1% (229 patients) over 4 months, with irritation between the two comparators (less than BPO, more than clindamycin)  [12]. A vehicle-controlled trial in 60 patients showed a three-fold greater severity reduction than placebo  [13].
For adult female acne, 15% gel was non-inferior to adapalene 0.1% over 9 months with significantly less dryness and scaling, and continuing past 3 months held results better than stopping  [14]. The European program overview adds two clinically important negatives: no teratogenicity signal and no induction of P. acnes resistance, which is why azelaic acid keeps its place as antibiotic-sparing therapy  [15].

## Melasma and dark marks: real wins, honestly ranked
The head-to-head record against hydroquinone is genuinely strong and genuinely old. In the largest trial (329 women, 24 weeks, double-blind, both arms with sunscreen), 20% azelaic acid produced good or excellent results in 65% with NO significant differences versus hydroquinone 4% on any efficacy measure, and no allergic sensitization or ochronosis  [16]. Against the weaker 2% hydroquinone it was clearly superior: 73% versus 19% good-to-excellent in 155 patients  [17]. A small 2-month open trial even favored azelaic acid over hydroquinone 4% on MASI, though its authors flagged the open design and called for larger studies  [18].
Now the ranking honesty. A 2021 network meta-analysis of 59 randomized trials put azelaic acid 8th of 14 melasma therapies, behind lasers, triple combination cream, topical vitamin C and oral tranexamic acid; combination therapy beat monotherapy in 87% of studies comparing them  [20]. A 2019 systematic review gave its strong recommendations to cysteamine, triple combination therapy and tranexamic acid, not azelaic acid  [21]. Equal to hydroquinone 4% in its best trial, mid-field in the modern league table: both are true, and a page that tells you only one of them is selling something.
Post-inflammatory hyperpigmentation, the dark marks acne leaves in brown and black skin, has exactly one direct azelaic acid study: a 16-week open-label baseline-controlled pilot of 15% gel that reduced both acne and PIH  [19]. Promising, uncontrolled, and thin: that is the entire direct PIH evidence base. The tyrosinase-inhibition rationale is real but preclinical  [23].

## The viral claims: hair loss, fungal acne, and what the searches return
DHT and hair loss. The claim that azelaic acid blocks DHT traces to one 1988 in vitro study: potent 5 alpha-reductase inhibition in skin homogenates, whose authors conditioned everything on in vivo confirmation  [24]. Our search for azelaic acid trials in androgenetic alopecia returns no randomized monotherapy trial: reviews, a case report, a minoxidil combination study, and one pilot in a different disease  [50]. That pilot randomized 31 people with patchy alopecia AREATA (autoimmune, not androgenetic) to 20% azelaic acid or anthralin and found similar regrowth with no vehicle arm  [36]. If you are buying azelaic acid to protect your hairline, you are betting on a 37-year-old test-tube result.
Fungal acne. Malassezia folliculitis trials of azelaic acid: none found. Our searches return in vitro work, reviews and case reports, not treatment trials  [51]. The irony is that the Malassezia connection is real, just backwards: the yeast PRODUCES azelaic acid, and the molecule's entire dermatologic career began when researchers isolated tyrosinase-inhibiting dicarboxylic acids from Malassezia cultures in 1978  [30,23]. Plausible pharmacology, zero clinical trials: that is the grade.
Skin aging. The 2023 systematic review looked for eligible randomized trials of azelaic acid for skin aging and found none  [22].

## Is azelaic acid safe?
For most users, yes, within the label's boundaries, and the pharmacokinetics explain why: about 4% systemic absorption, plasma levels that stay inside the normal dietary range even with twice-daily prescription gel, and a molecule your body already makes and eats  [40,38]. The 15% gel lists NO contraindications; Azelex is contraindicated only in component hypersensitivity  [38,40].
Safe does not mean comfortable. Roughly one user in three of the 15% gel gets burning, stinging or tingling, and the label sections below quantify every reaction the trials and postmarketing reports documented  [38]. Pediatric safety is not established for any of the products  [38,40].

## What are the side effects?
The 15% gel's numbers, from 788 trial subjects: burning, stinging or tingling 29%, itching 11%, scaling or dry skin 8%, redness or irritation 4%  [38]. Most reactions were mild (16% of subjects) or moderate (9%); severe burning affected 4%  [38]. In the active-controlled trial the gel caused more overall adverse reactions than metronidazole (19.4% versus 7.1%)  [38].
The foam runs milder in its trials: application site pain 6.2% versus 1.5% for vehicle, itching 2.5%, dryness and redness under 1%  [39]. Azelex reports its most common reactions (pruritus, burning, stinging, tingling) in only 1 to 5% of patients, attributes early stinging partly to the molecule's low pH, and notes it commonly subsides with continued use  [40].
Context for the sting: irritation clusters in the first few weeks and usually settles  [38,40]. In dermal safety studies the gel was more irritating than its own vehicle, and no phototoxicity or photoallergy was seen  [38].

## Who needs to be careful?
Darker skin: isolated cases of hypopigmentation (light spots) have been reported, and the labels say plainly that azelaic acid has not been well studied in patients with dark complexions; monitor for early pigment changes and report them  [38,40]. Weigh that against the PIH data above: the population with the most to gain is the one with the least dedicated safety study.
Asthma: worsening of asthma has been reported with azelaic acid formulations, prominently enough that the gel label gives it a dedicated warning  [38]. Postmarketing reports also include hypersensitivity reactions: angioedema, eye and facial swelling, dyspnea, urticaria, wheezing  [38].
Eyes and mucous membranes: keep it away from them; accidental eye exposure has caused iridocyclitis. Rinse thoroughly with water on contact and get care if irritation persists  [38].
Rarities on the record: vitiligo depigmentation, small depigmented spots, hypertrichosis, keratosis pilaris-type reddening, and flare of cold sores  [38]. The foam adds a physical hazard: it is flammable and pressurized  [39].

## Can you use azelaic acid during pregnancy or breastfeeding?
Azelaic acid is one of the few actives dermatology reviews actually recommend in pregnancy: a peer-reviewed review of acne treatment in pregnancy names topical azelaic acid or benzoyl peroxide as baseline therapy  [35]. Here is what the primary documents say underneath that recommendation, because the two labels frame it differently.
The modern gel label reasons from exposure: azelaic acid is minimally absorbed, maternal use is not expected to result in fetal exposure, and the animal embryofetal toxicity seen orally occurred only at maternally toxic doses 19 to 162 times the human dose, without malformations  [38]. The older Azelex label is more conservative with the same data: no adequate and well-controlled studies in pregnant women, so use only if clearly needed  [40]. Both are honest; neither is a human trial, because there are none.
Breastfeeding: azelaic acid is naturally present in human milk already, and with under 4% absorption the labels expect no meaningful change in milk levels, while Azelex still advises caution  [38,40]. For contrast, the melasma alternative hydroquinone is the one a pregnancy-safety review singles out for relatively high systemic absorption  [34]. Decisions here belong with your clinician; this page's job is to show you what the documents actually say.

## Does azelaic acid cause purging, and how long until results?
Purging, the idea that a treatment makes skin worse before better, is not a measured endpoint in any azelaic acid trial we cite. What the trials and labels do document in the early weeks is sensory irritation: burning, stinging and tingling that clusters at the start and usually settles  [38,40]. If azelaic acid has a retinoid-style comedonal purge, no controlled study has quantified it, and we will not pretend otherwise.
Timelines, from the documents rather than from influencers: acne improvement in the majority of patients within 4 weeks per the Azelex label, with trials running 3 to 6 months  [40,9]. Rosacea trials ran 12 to 15 weeks, and the label says to reassess the diagnosis if 12 weeks brings no improvement  [38]. Melasma head-to-heads ran 24 weeks, with one small open trial showing separation from hydroquinone by month 2  [16,18]. Adult-acne maintenance data suggest staying on it: stopping at 3 months lost ground versus continuing to 9  [14].

## What interacts with azelaic acid?
The labels list no drug-drug interactions; none of the three has a drug interactions section at all  [38,40,39]. That is an absence of studied interactions, not a certificate that combinations are safe.
What the labels DO restrict is product pairings: avoid alcoholic cleansers, tinctures and astringents, abrasives and peeling agents, and occlusive dressings while using azelaic acid  [38]. In routine terms, that puts high-strength exfoliating acid toners and physical scrubs on the caution list during treatment, on label language rather than interaction studies. Popular pairing questions (niacinamide, vitamin C, retinoids) have no data in the labels or in our searches: no compatibility studies exist either way, and the schedule tool on this site says exactly that instead of inventing rules.

## Pharmacokinetics
About 4% of a topical dose is absorbed systemically; 3 to 5% of the applied dose penetrates the stratum corneum and up to 10% reaches viable epidermis and dermis  [40]. The topical half-life is about 12 hours against 45 minutes orally, meaning skin entry is the bottleneck, not clearance  [40].
Because azelaic acid is a dietary constituent with endogenous plasma levels of 20 to 80 ng/mL, systemic exposure from treatment disappears into the noise: twice-daily 15% gel produced plasma levels of 42 to 63.1 ng/mL, inside the range measured in vehicle-treated subjects  [40,38]. The foam PK study (21 patients, whole-face dosing at a measured 0.94 g per application) reached steady state by day 5 with mean peak levels of 51.8 ng/mL, again overlapping baseline  [39].
The clinically interesting delivery is local: follicular casts sampled after a single 20% cream application held azelaic acid at concentrations comparable to the levels that inhibit acne bacteria in vitro  [31]. Elimination is mainly unchanged in urine  [40].

## Storage and handling
Gel: 50 g tube, stored at 25 C with excursions 15 to 30 C. Azelex cream: 30 g or 50 g tube, protect from freezing, store on its side at 15 to 30 C. Foam: pressurized 50 g can; flammable; no fire, flame or smoking during and right after application; do not puncture or incinerate; keep below 120 F (49 C)  [38,40,39].

## Frequently asked questions
Rendered from the faq[] array; answers ship with inline citation anchors and 320-character answer summaries for the machine layer.

## References
All 52 citations render as a numbered list in n order; inline cite tokens resolve to these numbers. Fetch dates and verification method for every source live in the claims ledger; the structured citation manifest ships alongside this page  [6].

## Study results
| Study | Species/model | n | Duration | Outcome | Effect size |
| --- | --- | --- | --- | --- | --- |
| S01 (https://europepmc.org/article/MED/12789172) | human (Two identical multicenter, randomized, double-blind, vehicle-controlled phase III trials, 12 weeks) | 664 (333 gel, 331 vehicle); papers report 329 + 335 enrolled | 12 weeks | Mean inflammatory lesion reduction 57.9% vs 39.9% (study one) and 50.0% vs 38.2% (study two); IGA success (clear, minimal or mild) 61% vs 40% and 61% vs 48%; erythema improved in 44% vs 29% and 46% vs 28%. No serious treatment-related adverse events. | Absolute IGA success difference +21 and +13 percentage points vs vehicle |
| S02 (https://europepmc.org/article/MED/14623704) | human (Multicenter, double-blind, randomized, parallel-group active-comparator trial, 15 weeks) | 251 | 15 weeks | Azelaic acid superior: inflammatory lesions -72.7% vs -55.8%; erythema improved 56% vs 42%; metronidazole plateaued after week 8 while azelaic acid kept improving; overall adverse reactions 19.4% vs 7.1% favored metronidazole on tolerability. | -72.7% vs -55.8% lesion reduction (P<.001); nominal count -12.9 vs -10.7 (P=.003) |
| S03 (https://europepmc.org/article/MED/10365928) | human (Single-center, double-blind, randomized, contralateral split-face trial) | 40 | 15 weeks | Equal reductions in inflammatory lesions; significantly higher physician global-improvement rating for azelaic acid; trace stinging on application with azelaic acid; patient overall impression favored azelaic acid. | Equal lesion reduction; global improvement favored azelaic acid (significant) |
| S04 (https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=9fabd24e-4c3b-49a0-aa5f-c8d75ae67572) | human (Two multicenter, randomized, double-blind, vehicle-controlled trials, 12 weeks (phase 3 program)) | 1362 (681 foam, 681 vehicle) | 12 weeks | IGA success 32.1% vs 23.4% (trial 1) and 43.4% vs 32.5% (trial 2); mean inflammatory lesion change -13.2 vs -10.3 and -13.3 vs -9.5; both coprimary endpoints P<.001 in the published phase 3 report. Application site pain 6.2% vs 1.5%. | IGA success difference +8.7 and +10.9 percentage points vs vehicle |
| S05 (https://europepmc.org/article/MED/25919144) | human (Cochrane systematic review and meta-analysis, 106 RCTs) | 13,631 participants | Review (searches to July 2014) | Azelaic acid more effective than placebo in papulopustular rosacea, HIGH quality evidence (metronidazole moderate). Participant-assessed improvement RR 1.46 (95% CI 1.30 to 1.63). Head-to-head results between the two were contradictory across three studies. | RR 1.46 (95% CI 1.30 to 1.63) vs placebo, participant-assessed |
| S06 (https://europepmc.org/article/MED/30585305) | human (Updated systematic review with GRADE certainty assessments, 152 studies) | 20,944 participants | Review (searches to March 2018) | High-certainty evidence for topical azelaic acid and topical ivermectin for reducing papules and pustules; moderate certainty for topical metronidazole; brimonidine high certainty for erythema. | GRADE: high certainty (azelaic acid, papules and pustules) |
| S07 (https://europepmc.org/article/MED/40213532) | human (Frequentist network meta-analysis, 19 RCTs, moderate-to-severe papulopustular rosacea) | 8,208 participants | Review (2025) | Azelaic acid 20% ranked first for IGA improvement (OR 8.54, 95% CI 2.48 to 29.45; P-score 0.97). Azelaic acid 15% was the only agent with a statistically significant adverse-event odds ratio (1.95, 95% CI 1.30 to 2.93): best-in-class efficacy and worst-in-class sting in the same dataset. | OR 8.54 (2.48 to 29.45) for IGA improvement; AE OR 1.95 (1.30 to 2.93) |
| S08 (https://europepmc.org/article/MED/2528257) | human (3-month double-blind vehicle-controlled trial plus 6-month single-blind tretinoin comparison) | 92 (vehicle comparison); 289 (tretinoin comparison) | 3 and 6 months | Significantly more effective than vehicle in moderate inflammatory acne; equal to tretinoin 0.05% for comedonal acne with fewer local side effects than the retinoid. | Significant vs vehicle; equivalence vs tretinoin with better tolerability |
| S09 (https://europepmc.org/article/MED/2528256) | human (Placebo-controlled clinical and microbiological studies) | Not stated in abstract | 2+ months | Inflamed lesions reduced vs placebo after 1 month, non-inflamed after 2 months; skin-surface free fatty acids fell 15.9% to 10.5%; follicular Micrococcaceae reduced 2,500-fold and Propionibacterium species 44-fold; sebum excretion unchanged. | 2,500-fold and 44-fold microbial density reductions |
| S10 (https://europepmc.org/article/MED/2938615) | human (6-month double-blind comparison in men) | 45 | 6 months | Both beneficial with few minor side effects; oral tetracycline more effective, but the differences were only just significant. | Tetracycline advantage at the margin of significance |
| S11 (https://europepmc.org/article/MED/16281587) | human (Two independent randomized, blinded comparative trials, 4 months) | 351 (vs BPO 5%) and 229 (vs clindamycin 1%) | 4 months | As effective as benzoyl peroxide 5% and clindamycin 1%: median inflamed-lesion reductions 70% and 71%. Local burning and irritation distinctly less than BPO, more than clindamycin. | Median inflamed-lesion reduction 70% and 71% (equivalence) |
| S12 (https://europepmc.org/article/MED/17456913) | human (Double-blind randomized vehicle-controlled trial, 45 days) | 60 | 45 days | Total lesion count reduced 60.6% vs 19.9% for vehicle (P=0.002); acne severity index reduced 65.2% vs 21.3% (P=0.001). | Roughly 3-fold greater severity-index reduction than placebo |
| S13 (https://europepmc.org/article/MED/25399481) | human (Randomized investigator-blind parallel-group trial, treatment plus maintenance) | 55 women 18 to 45 | 9 months | Comparable lesion, severity and quality-of-life improvements; azelaic acid non-inferior for inflammatory lesions with significantly less dryness and scaling; continued 9-month use held results better than stopping at 3 months. | Non-inferior to adapalene; less dryness and scaling (P<0.05) |
| S14 (https://europepmc.org/article/MED/8654128) | human (Narrative overview of vehicle-controlled and comparative European trials) | Program-wide (multiple trials) | Review (1996) | Efficacy comparable to tretinoin 0.05%, benzoyl peroxide 5% and topical erythromycin 2%; non-teratogenic; excellent local tolerability; no induction of Propionibacterium acnes resistance. | Equivalence class with standard topicals |
| S15 (https://europepmc.org/article/MED/1816137) | human (24-week double-blind randomized comparison, both arms with broad-spectrum sunscreen) | 329 women | 24 weeks | 65% good or excellent results with azelaic acid; no significant treatment differences vs hydroquinone 4% on overall rating, lesion size or pigmentary intensity; no allergic sensitization or exogenous ochronosis observed with azelaic acid. | Equivalence vs hydroquinone 4% (65% good or excellent) |
| S16 (https://europepmc.org/article/MED/2528260) | human (Randomized double-blind comparison) | 155 patients of Indo-Malay-Hispanic origin | 24 weeks | Azelaic acid clearly superior to the low hydroquinone strength: good-to-excellent results 73% vs 19%. | +54 percentage points good-to-excellent vs hydroquinone 2% |
| S17 (https://europepmc.org/article/MED/22151936) | human (Open comparative trial, 2 months) | 29 women | 2 months | MASI fell further with azelaic acid (7.6 to 3.8) than hydroquinone (7.2 to 6.2), significant at month 2; authors caution the trial was open and small and call for larger studies. | MASI difference significant (95% CI 0.03 to 4.9), open design |
| S18 (https://europepmc.org/article/MED/21637899) | human (16-week open-label baseline-controlled pilot in acne with PIH, darker skin types) | Pilot cohort (not stated in abstract) | 16 weeks | Reduced both acne and post-inflammatory hyperpigmentation from baseline. No randomized vehicle-controlled PIH trial of azelaic acid exists. | Baseline-controlled improvement only (no comparator) |
| S19 (https://europepmc.org/article/MED/34660626) | human (Network meta-analysis of 59 RCTs, 14 therapies, MASI endpoint) | 59 RCTs | Review (searches to December 2020) | Azelaic acid ranked 8th of 14 therapies for efficacy vs placebo, behind lasers, triple combination cream, topical vitamin C and oral tranexamic acid; combination therapy beat monotherapy in 87% of studies comparing them. | Mid-field ranking (8 of 14) |
| S20 (https://europepmc.org/article/MED/31741361) | human (Systematic review of 35 RCTs of topical melasma treatments) | 35 RCTs | Review (searches to March 2019) | Strong clinical recommendations went to cysteamine, triple combination therapy and tranexamic acid, not azelaic acid; azelaic acid is one of many agents with supportive but not top-tier evidence. | Not among the strongly recommended agents |
| S21 (https://europepmc.org/article/MED/37550898) | human (Systematic review with meta-analyses, 43 RCTs of at least 6 weeks) | 43 RCTs | Review (searches to December 2022) | More effective than vehicle for rosacea, acne and melasma; better than metronidazole 0.75% on erythema and lesions; better than hydroquinone 2% for global improvement; comparisons with other actives often equivalent; NO eligible skin-aging RCTs found. | Significant vs vehicle across the three indications |
| S22 (https://europepmc.org/article/MED/16343028) | human (Randomized active-comparator pilot, no vehicle arm, 12 weeks plus 8-week follow-up) | 31 (15 azelaic acid, 16 anthralin) | 20 weeks total | Complete regrowth response 53.3% vs 56.2% (not significant). Without a vehicle arm the trial cannot show either drug beats no treatment; alopecia areata is an autoimmune condition distinct from androgenetic hair loss. | No difference vs anthralin (p > 0.05) |
| S23 (https://europepmc.org/article/MED/42572367) | human (Randomized vehicle-controlled split-face cosmetic study of a retinal 0.1% + azelaic acid 10% combination) | 23 completers, ages 16 to 49 | 8 weeks | Imaging endpoints improved vs vehicle: texture +5.6%, surface irregularities -12.7%, overall redness -18.1%, pores +22.3%. Cosmetic endpoints, combination product: the azelaic acid contribution cannot be isolated, and this is the ONLY randomized human data at the 10% strength in this table. | Texture +5.6% vs vehicle (p=0.0016); redness -18.1% (p=0.011) |
| S24 (https://europepmc.org/article/MED/8217752) | human (In vivo follicular-cast sampling after a single application) | 9 young adults | 5 hours | Follicular-cast azelaic acid reached concentrations comparable to those required to inhibit P. acnes and S. epidermidis growth in vitro, supporting follicular antimicrobial delivery despite low systemic absorption. | Follicular concentrations in the in vitro inhibitory range |
| S25 (https://europepmc.org/article/MED/99481) | in vitro (Enzyme kinetics of dicarboxylic acids isolated from Pityrosporum cultures) | n/a | n/a | Dicarboxylic acids including azelaic acid act as competitive inhibitors of tyrosinase in vitro; the authors proposed use in hyperpigmentary disorders. This 1978 paper is the origin of azelaic acid dermatology. | Competitive enzyme inhibition (kinetics) |
| S26 (https://europepmc.org/article/MED/3207614) | in vitro (In vitro human-skin enzyme assay with tritiated testosterone) | n/a | n/a | Potent 5 alpha-reductase inhibition in the test tube, detectable at 0.2 mmol/l, complete at 3 mmol/l. The authors conditioned clinical relevance on in vivo confirmation, which has never come: this row is the entire basis of the DHT-blocker claim. | Complete enzyme inhibition at 3 mmol/l (in vitro only) |
| S27 (https://europepmc.org/article/MED/1726169) | in vitro (In vitro antimicrobial characterization against P. acnes strain P37) | n/a | n/a | Bactericidal at 500 mM in pH 6 buffer, growth inhibition at 100 microM in defined medium; activity strongly pH-dependent, greatest in acid conditions; protein synthesis the most sensitive target. | Growth inhibition at 100 microM (defined medium) |
| S28 (https://europepmc.org/article/MED/7829407) | in vitro (Transmembrane pH-gradient studies in continuous culture) | n/a | n/a | Dissipated the transmembrane proton gradient of P. acnes and S. epidermidis; rapid loss of viability at pH 4.0 with no viable cells at 60 minutes, little effect at pH 6.0: antibacterial action tied to acidic skin surface conditions. | delta pH reduced up to 88%; complete kill at pH 4.0 in 60 min |
| S29 (https://europepmc.org/article/MED/20545756) | in vitro (UVB-stimulated normal human keratinocytes, PPARgamma pathway) | n/a | n/a | Suppressed UVB-induced IL-1beta, IL-6 and TNF-alpha; reduced NF-kB p65 nuclear translocation; effects abolished by a PPARgamma antagonist, identifying PPARgamma activation as the anti-inflammatory mechanism. | Cytokine suppression at 20 mM, PPARgamma-dependent |

## What we do not know yet
What we do not know, stated plainly. Direct evidence at the 10% cosmetic strength is close to absent: every monotherapy trial in our table used 15% or 20%, and the only randomized data at 10% is an 8-week, 23-person split-face study of a retinal combination measuring texture and redness, not acne, rosacea or melasma outcomes. Long-term melasma data are limited: the head-to-head hydroquinone trials ran 24 weeks, maintenance beyond that is uncharacterized, and modern evidence syntheses rank other agents first. For rosacea, efficacy against erythema without papules and pustules has not been evaluated, by the label's own statement. The labels also state azelaic acid has not been well studied in people with dark complexions, which matters because that is exactly who post-inflammatory hyperpigmentation affects most, and the PIH evidence itself is a single open-label pilot. Pediatric safety is not established. The clinical mechanism is unknown per FDA labeling. The DHT and fungal-acne claims popular in skincare content rest on in vitro work and searches that return no clinical trials. Purging is not a measured endpoint in any azelaic acid trial we cite: what the trials measured is early-weeks stinging and irritation, which usually settles.

## Questions and answers
### Is azelaic acid FDA approved?
Yes, at prescription strengths. Finacea 15% gel and foam are approved for rosacea papules and pustules, Azelex 20% cream for inflammatory acne, plus generic 15% gels. The 10% serums sold over the counter are cosmetics, not approved drugs.

Yes, but only the prescription products. FDA has approved azelaic acid three times: Finacea 15% gel (NDA 021470) and Finacea Foam 15% (NDA 207071) for the inflammatory papules and pustules of mild to moderate rosacea, and Azelex 20% cream (NDA 020428) for mild-to-moderate inflammatory acne, plus several generic 15% gels. The azelaic acid serums on cosmetics shelves are a different legal object: cosmetics do not receive FDA premarket approval, and azelaic acid is not an ingredient in FDA's over-the-counter acne monograph, so no OTC azelaic acid product is an approved drug at any strength.

### What is the difference between prescription azelaic acid and 10% serums?
Concentration, vehicle, and evidence. Prescriptions are 15 to 20% drugs whose trials produced the efficacy data. Serums are about 10%, regulated as cosmetics, and no randomized trial tests a 10% serum alone for acne, rosacea or melasma.

Three differences stack. Concentration: prescriptions carry 15% or 20% azelaic acid; serums usually about 10%. Regulation: the prescriptions are FDA-approved drugs with reviewed manufacturing; the serums are cosmetics with no premarket review. Evidence: every azelaic acid monotherapy trial in our table used 15% or 20%. At 10%, the only randomized human data we could find is an 8-week, 23-person split-face cosmetic study of a retinal combination measuring texture and redness, which cannot isolate the azelaic acid. When a serum cites azelaic acid research, it is borrowing prescription-strength evidence.

### Does azelaic acid work for rosacea?
Yes, for papules and pustules, with high-certainty evidence: pivotal trials in 664 and 1362 subjects beat vehicle, it beat metronidazole head-to-head, and Cochrane rates the evidence high quality. Redness without bumps was never evaluated.

For inflammatory papules and pustules, azelaic acid has some of the best evidence in topical dermatology. Two pivotal vehicle-controlled programs (664 gel subjects, 1362 foam subjects) showed roughly 50 to 58% lesion reductions and superior global success. Head-to-head, 15% gel beat metronidazole 0.75% (72.7% versus 55.8% lesion reduction). Cochrane rates the placebo-superiority evidence HIGH quality, and the 2019 GRADE update keeps it high certainty; a 2025 network meta-analysis ranks 20% first in class for IGA improvement. The boundary: efficacy for erythema without papules and pustules has not been evaluated, per the label itself. Flushing-only rosacea is outside this drug's evidence.

### Is azelaic acid as good as benzoyl peroxide for acne?
In the direct trial, yes: 15% gel matched benzoyl peroxide 5% (70% median lesion reduction, 351 patients) and clindamycin 1%, with less irritation than BPO. It also equaled tretinoin 0.05% and does not breed resistant bacteria.

The head-to-head data say equivalence. In two randomized blinded trials, 15% azelaic acid gel matched benzoyl peroxide 5% gel (median inflamed-lesion reduction 70%, 351 patients) and clindamycin 1% gel (71%, 229 patients) over 4 months, with local irritation distinctly less than BPO and more than clindamycin. The 20% cream separately equaled tretinoin 0.05% for comedonal acne with better tolerability, and came just short of oral tetracycline. Two practical differentiators from the European program review: azelaic acid is non-teratogenic and does not induce resistance in P. acnes, which keeps it useful where antibiotics and retinoids are unwelcome.

### Is azelaic acid as effective as hydroquinone for melasma?
In its biggest trial, 20% azelaic acid matched hydroquinone 4%: 65% good or excellent results over 24 weeks, no significant differences, no ochronosis. But modern reviews rank other options (triple cream, tranexamic, cysteamine) above both.

Against hydroquinone itself, the record is strong: in a 24-week double-blind trial of 329 women (both arms with sunscreen), 20% azelaic acid produced 65% good or excellent results with no significant differences from hydroquinone 4%, and none of hydroquinone's ochronosis risk appeared. It clearly beat hydroquinone 2% (73% versus 19%), and a small open trial favored it over 4% at two months. The honest frame: a 2021 network meta-analysis of 59 trials ranks azelaic acid 8th of 14 melasma therapies, and the 2019 systematic review's strong recommendations went to cysteamine, triple combination cream and tranexamic acid instead. Azelaic acid is a legitimate hydroquinone alternative, especially where hydroquinone is unwanted; it is not the current first choice of the evidence.

### Can I use azelaic acid while pregnant or breastfeeding?
It is the acne active reviews recommend as baseline in pregnancy. Absorption is about 4%, the gel label expects no fetal exposure, and animal harm appeared only at maternally toxic oral doses. No human trials exist; involve your clinician.

Azelaic acid is the topical a peer-reviewed pregnancy review recommends as baseline acne therapy (alongside benzoyl peroxide), while oral retinoids are absolutely contraindicated. The basis: roughly 4% absorption, plasma levels inside the normal dietary range, and a modern gel label stating maternal use is not expected to result in fetal exposure; oral animal studies produced embryofetal toxicity only at maternally toxic doses 19 to 162 times the human dose, with no malformations. The older Azelex label reads more conservatively: no adequate human studies, use only if clearly needed. Breastfeeding: azelaic acid is already naturally present in human milk, and the labels expect no meaningful change from topical use, with Azelex advising caution. There are no controlled human pregnancy trials; make the call with your clinician, not with a serum marketing page.

### Does azelaic acid cause purging, and why does it sting?
No trial measures purging; what is measured is early irritation: burning, stinging or tingling in 29% with 15% gel, mostly first weeks, usually settling. The sting is partly the molecule's low pH. Severe persistent irritation means stop and reassess.

Purging is influencer vocabulary, not trial vocabulary: no azelaic acid study we cite measured a worse-before-better lesion phase. What the controlled data quantify is sensory irritation, front-loaded in the first few weeks: burning, stinging or tingling in 29% of 15% gel users (severe in 4%), itching in 11%, versus far lower vehicle rates. The foam and the 20% cream run milder in their own trials (site pain 6.2%; common reactions 1 to 5%). The Azelex label attributes the initial sting partly to azelaic acid's low pH and notes it commonly subsides with continued treatment; the labels' stop rule is sensitivity or severe irritation that persists. A 2025 network meta-analysis confirms the trade honestly: azelaic acid tops the rosacea efficacy ranking and also carries the only significant adverse-event signal among the topicals.

### How long does azelaic acid take to work?
From the documents: acne improves in the majority within 4 weeks per the Azelex label ; rosacea trials ran 12 to 15 weeks and the label says reassess at 12 ; melasma head-to-heads ran 24 weeks.

The trial clocks, condition by condition. Acne: the Azelex label states improvement occurs in the majority of patients with inflammatory lesions within four weeks; its controlled trials ran 3 to 6 months. Rosacea: the pivotal trials ran 12 weeks (15 for the metronidazole comparison, where azelaic acid was still improving at the end while metronidazole had plateaued by week 8), and the label instructs reassessing the diagnosis if 12 weeks brings nothing. Melasma: the double-blind hydroquinone comparisons ran 24 weeks; one small open trial saw significant separation by month 2. Adult female acne: continuing to 9 months held results better than stopping at 3. Expect a season, not a fortnight.

### How much azelaic acid should I apply?
The labels say a thin layer twice daily. Quantified: the foam PK study measured 0.94 g per whole-face dose, and the fingertip-unit standard allots 2.5 FTU (about 1.25 g) for face and neck.

All three labels prescribe a thin layer twice daily, morning and evening, on cleansed, dried skin. Two published numbers turn thin layer into grams. The foam label's pharmacokinetic study measured a mean of 0.94 g of foam (141 mg azelaic acid) per whole-face application. And the dermatology-standard fingertip unit (the 0.5 g ribbon from fingertip to first crease; 4 hand areas = 2 FTU = 1 g) allots 2.5 FTU for face and neck, one FTU covering about 286 square centimeters. Our application-quantity tool does the arithmetic: pick zones, get grams per application, per week, and how long your tube lasts at label frequency. A 50 g tube at about 1 g twice daily runs out in roughly 25 days, which is worth knowing before a 12-week course.

### Does azelaic acid treat fungal acne (Malassezia folliculitis)?
No clinical trials exist: our searches return in vitro work and reviews, no treatment trials. The Malassezia link is real but backwards: the yeast produces azelaic acid, which is how the molecule was discovered in 1978.

The claim has plausible pharmacology and zero clinical trials. Searches for azelaic acid with Malassezia or pityriasis versicolor return mechanism papers, reviews and case reports, and no trial of azelaic acid for Malassezia folliculitis. The genuinely interesting part is the direction of the relationship: Malassezia produces azelaic acid, and the molecule entered dermatology when researchers isolated tyrosinase-inhibiting dicarboxylic acids from Pityrosporum cultures in 1978 while studying why tinea versicolor leaves light patches. If you have suspected Malassezia folliculitis, the evidence-backed treatments are antifungals; azelaic acid for that use is an untested extrapolation, and pages telling you otherwise are grading vibes, not trials.

### Does azelaic acid block DHT or help hair loss?
The DHT claim rests on one 1988 test-tube study of 5 alpha-reductase inhibition. No randomized trial of azelaic acid alone for pattern hair loss exists ; the only pilot was in alopecia areata, a different disease.

In vitro, yes: a 1988 study found azelaic acid potently inhibits 5 alpha-reductase in human skin homogenates, completely at 3 mmol/l. Its authors wrote that clinical use would depend on confirming the effect in vivo. That confirmation has not arrived in 37 years. In people: our search for azelaic acid trials in androgenetic alopecia returns no randomized monotherapy trial, only reviews, a case report and a minoxidil combination study. The closest human data is a 31-person pilot in patchy alopecia AREATA, an autoimmune condition unrelated to DHT, where 20% azelaic acid matched anthralin with no vehicle arm to show either worked. Products marketing azelaic acid as a topical DHT blocker are extrapolating from a test tube.

### Is azelaic acid safe for darker skin tones?
Mostly encouraging, honestly incomplete: it treats PIH in a 16-week open pilot and beat hydroquinone 2% in 155 Indo-Malay-Hispanic patients, but labels report isolated hypopigmentation and say dark complexions were not well studied.

Two true things need holding together. Azelaic acid is actively useful in skin of color: the melasma trial in 155 patients of Indo-Malay-Hispanic origin showed 73% good-to-excellent results, and the one direct PIH study (16-week open-label pilot, darker skin types) reduced both acne and the dark marks it leaves. Unlike hydroquinone, no exogenous ochronosis was seen in its biggest melasma trial. And: the labels report isolated cases of hypopigmentation, state plainly that azelaic acid has not been well studied in patients with dark complexions, and instruct monitoring for early pigment change. A tyrosinase inhibitor that fades dark patches can, rarely, lighten where you did not ask it to. Watch your skin, and report changes.

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38. AZELAIC ACID gel, for topical use (NDA 021470; originally approved as FINACEA) https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=66178511-5c1a-4ecd-bc98-2ceb54e710ac
39. FINACEA FOAM (azelaic acid) aerosol, foam, for topical use (NDA 207071) https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=9fabd24e-4c3b-49a0-aa5f-c8d75ae67572
40. AZELEX (azelaic acid cream) 20% (NDA 020428) https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ebdfcaf7-b5d6-47e1-be87-ccaba4b97e75
41. Drugs@FDA record for NDA 021470 (FINACEA, azelaic acid gel 15%) https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021470
42. Drugs@FDA record for NDA 020428 (AZELEX, azelaic acid cream 20%) https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020428
43. Drugs@FDA record for NDA 207071 (FINACEA FOAM, azelaic acid foam 15%) https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=207071
44. Drugs@FDA API query: products.active_ingredients.name azelaic acid (9 applications) https://api.fda.gov/drug/drugsfda.json?search=products.active_ingredients.name:%22azelaic%20acid%22&limit=20
45. openFDA label query: openfda.generic_name azelaic acid (self-registered OTC-style listings at 10 to 15%) https://api.fda.gov/drug/label.json?search=openfda.generic_name:%22azelaic%20acid%22&limit=10
46. 21 CFR Part 333 Subpart D: Topical Acne Drug Products (permitted active ingredients) https://www.ecfr.gov/current/title-21/chapter-I/subchapter-D/part-333/subpart-D
47. FDA Authority Over Cosmetics: How Cosmetics Are Not FDA-Approved, but Are FDA-Regulated https://www.fda.gov/cosmetics/cosmetics-laws-regulations/fda-authority-over-cosmetics-how-cosmetics-are-not-fda-approved-are-fda-regulated
48. Compounding and the FDA: Questions and Answers https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers
49. PubChem compound record CID 2266: Azelaic acid (nonanedioic acid) https://pubchem.ncbi.nlm.nih.gov/compound/2266
50. PubMed query: azelaic acid AND (androgenetic alopecia OR hair loss) AND (randomized OR trial); 6 results, none a monotherapy RCT https://pubmed.ncbi.nlm.nih.gov/?term=azelaic+acid+AND+%28androgenetic+alopecia+OR+hair+loss%29+AND+%28randomized+OR+trial%29
51. PubMed queries: azelaic acid AND Malassezia; azelaic acid AND pityriasis versicolor; no clinical trials of azelaic acid for Malassezia folliculitis https://pubmed.ncbi.nlm.nih.gov/?term=azelaic+acid+AND+Malassezia
52. PubMed query: azelaic acid 10% AND (randomized OR trial); 2 results, no 10% monotherapy RCT for acne, rosacea or melasma https://pubmed.ncbi.nlm.nih.gov/?term=%22azelaic+acid+10%25%22+AND+%28randomized+OR+trial%29