Porecelain

Flawless skin starts with the fine print.

Azelaic Acid

Azelaic acid rates Clear, but the rating is a judgement rather than a reading: we identified no comedogenicity assay of azelaic acid in any of the numeric papers we hold, and we could trace no primary assay behind the 0 that ingredient checkers print. What it has instead points the other way from a comedogenic finding — it is a comedolytic that dermatology guidelines recommend to treat acne, and vehicle-controlled trials have reported it reducing comedone counts rather than raising them. Those were treatment trials, not comedone-induction assays, so they reassure without running the exact test the word "comedogenic" asks for.

Clear Moderate confidence No legacy score. It does not appear in the assay corpus we searched.

AAD 2024 conditionally recommends it for acne; a 1989 trial counted comedones directly.

What it is

Azelaic acid is a straight-chain saturated dicarboxylic acid — a nine-carbon chain with a carboxyl group at each end. Its formula is C9H16O4 and its molecular weight is about 188 g/mol; its other names are nonanedioic acid and 1,7-heptanedicarboxylic acid. Fitton and Goa's pharmacological review describes it as a naturally occurring saturated dicarboxylic acid; the further details often repeated about it — that it is found in cereal grains, and that the skin yeast Malassezia furfur generates C8–C12 dicarboxylic acids — we carry at review level rather than from a primary source we read, and neither bears on comedogenicity. Unlike almost everything in the comedogenicity literature, it is not an oil, a wax, a fatty alcohol or an ester used to give a formula slip — it is an active drug, formulated to do something to the skin rather than to condition it. Its documented activities are anti-keratinising, antibacterial, anti-inflammatory and antimelanogenic, which is why it is used to treat acne, papulopustular rosacea and hyperpigmentation. On a label it appears as Azelaic Acid. Two classes of near neighbour share part of the name and are not this material: its salts and derivatives (potassium azeloyl diglycinate, dipotassium azelate and similar), and any finished product formulated with azelaic acid in it. Nothing on this page transfers to those.

Why we rate it Clear

We rate azelaic acid Clear at Moderate confidence. Clear here is a risk classification rather than a measured pass, and the Moderate records where the evidence sits: there is real human data, but it comes from treatment trials rather than from a comedogenicity assay, because we identified no comedogenicity assay of this material in the sources and searches reviewed for this page. Start with what is absent, because it decides the shape of the page. We identified no comedogenicity assay of azelaic acid in the numeric papers we hold. Fulton's 1989 rabbit-ear table, the source of most comedogenic numbers now in circulation, has no azelaic acid, nonanedioic acid or dicarboxylic-acid row anywhere in its 220 rows, which we read off a 400dpi render. Morris and Kwan's 1983 assay, an independent laboratory on the same 0–5 scale, tested 32 materials — seven lanolins, nine vegetable oils, eleven esters and five surfactants — and azelaic acid is not among them. Nguyen, Dang and Maibach's 2007 rabbit-ear study, on a 0–4 scale, names its fourteen test materials in its abstract, and azelaic acid is not one of them. Our own index of the legacy corpus files azelaic acid under never tested. So the 0 that consumer checkers print for it is not a measurement we can trace to any primary assay, and a 0 sitting in the same column as coconut butter's measured 4 invites a reader to treat an untested ingredient as a tested and cleared one. That is why our legacy score field is blank rather than zero. What azelaic acid has, and most untested ingredients do not, is a body of controlled human evidence pointing firmly the reassuring way — and pointing at the right lesion. It is a recognised acne treatment, not a suspected cause. The American Academy of Dermatology's 2024 acne guideline conditionally recommends topical azelaic acid for acne, a recommendation the panel grades on moderate-certainty evidence from randomised trials, and describes it as a comedolytic, antibacterial and anti-inflammatory agent. The mechanism that matters most here is the first of those: azelaic acid is reported to normalise the disturbed keratinisation of the follicle — the same follicular hyperkeratosis that begins a comedone — with the pharmacology review by Fitton and Goa (1991) summarising its effect on follicular keratinisation and its efficacy in comedonal as well as inflammatory acne. And the clinical endpoint is unusually close to the question. Comedogenicity is about comedones, and the azelaic acid acne trials counted them. The load-bearing citation is a primary trial report, not a summary of one: Katsambas, Graupe and Stratigos (1989) report a three-month double-blind study of 20% azelaic acid cream against its own vehicle in 92 patients, and a single-blind study in 289 patients with comedonal acne in which azelaic acid was as effective as 0.05% tretinoin at reducing comedones and better tolerated. A material that lowers comedone counts over months of twice-daily use on acne-prone faces is not behaving like a comedogen. That is the substance of the Moderate: a named guideline, plus trials that measured the exact lesion and found it going down. What keeps it from High is that none of this is a comedogenicity assay, and the distinction is real enough to spell out in the limits below.

What the evidence doesn’t tell you

The reassuring evidence and the comedogenic question are close, but they are not the same test, and the gap runs in the flattering direction — which is the direction to distrust. The trials measured the reduction of comedones in people who already had comedonal acne. A comedogenicity assay measures the opposite operation: whether applying a material to clear follicles induces comedones that were not there. We identified no study that applied azelaic acid to comedone-free skin to test induction. "Reduces existing comedones" and "does not create new ones" point the same way and are not the same finding, and a treatment that clears a lesion is strong but indirect evidence that it does not cause it. The trials also tested finished 20% and 15% creams and gels, not the isolated ingredient, so their results are about those products at those strengths, and a result about a formulation is not a dose–response curve for a molecule. That caveat has a limit worth stating fairly: because the double-blind comparison was against the cream's own vehicle, the difference between the arms is attributable to the 20% azelaic acid added to it, so this is not the usual finished-formula problem where nothing can be pinned on any one ingredient. What it does not give is a curve — no intermediate strengths were tested, so the result speaks for 20% and not for whatever fraction a cosmetic serum contains. The AAD recommendation is a treatment recommendation: it says azelaic acid is useful against acne, which is an efficacy judgement, not a measurement of comedogenic potential. The 1996 Cutis overview that summarises the same programme carries manufacturer authorship (Zaumseil was with Schering AG, which developed the drug); we cite it as a secondary summary and rest the comedone-count claim on the primary trial report instead. Azelaic acid is not side-effect-free, and Clear is a comedogenicity verdict, not a tolerability one: its common local effects are stinging, burning, itching and dryness in the first weeks of use, and it is those, not comedones, that make people stop it. None of that is pore-plugging, but a reader should not read Clear as "does nothing on the skin." Finally the bounds on the absence. An audit can establish that no assay of azelaic acid turned up in the papers we hold and the searches we ran; it cannot establish that none was ever run anywhere. We found no report of azelaic acid inducing comedones, but that is an absence of findings in what we read, not proof of an absence in the literature. Beyond this ingredient, a 2025 review of the field reports that no standardised comedogenicity test exists at all and that "non-comedogenic" is an unregulated label — a ceiling on how much any comedogenic number, present or absent, can be asked to carry.

Where you’ll see it

On a label it appears as Azelaic Acid. It is used as an active rather than as a texture ingredient, so it is the point of the product rather than a supporting player. The strengths that appear in the clinical literature and in the AAD guideline are 15% and 20%; lower-strength cosmetic serums and creams are sold without a prescription, and we have not audited what those contain. Those clinical strengths are far above the concentrations at which the emollients on the comedogenic charts are typically used, which is one more reason the material does not belong in the same mental column as them. Where azelaic acid sits in an ingredient list is not a comedogenicity signal, and there is no measured number to read off its position in any case.

Sources

Each source says what it actually is. Several widely-cited “sources” for comedogenic ratings are republishing the same 1989 assay, and counting them as independent agreement is how a thin evidence base gets made to look thick.

  1. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The rabbit-ear survey most online comedogenic numbers descend from. Method: ingredient diluted to roughly 10% in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, follicles scored for keratosis on a 0–5 scale whose own key reads 0–1 "not considered significant," 2–3 "borderline," 4–5 "considered positive." Read here off a 400dpi render of the journal scan rather than through a list quoting it. Cited purely for an absence: its 220 rows contain no azelaic acid, nonanedioic acid or dicarboxylic-acid entry. It supports no rating of azelaic acid in either direction.
  2. Morris WE, Kwan SC. "Use of the rabbit ear model in evaluating the comedogenic potential of cosmetic ingredients." J Soc Cosmet Chem 34:215–225 (1983) An independent laboratory's rabbit ear-canal assay on the same 0–5 scale, three rabbits, materials applied undiluted unless stated, 14 applications, graded microscopically. It predates Fulton 1989 and contradicts it in print on several materials, so it is not a republisher of him. Its 32 test materials are seven lanolins, nine vegetable oils, eleven esters and five surfactants. Cited for an absence: azelaic acid is not among them.
  3. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287–292 (2007) A later rabbit ear-canal study on a 0–4 scale — a third scale, easy to misread as Fulton's. Its abstract names all fourteen test materials (isopropyl palmitate, isopropyl myristate, butyl stearate, isopropyl isostearate, decyl oleate, isostearyl neopentanoate, isocetyl stearate, myristyl myristate, cocoa butter, cetyl alcohol, paraffin, stearyl alcohol, sodium lauryl sulfate, petrolatum). Cited for an absence: azelaic acid is not one of them.
  4. Reynolds RV, Yeung H, Cheng CE, et al. "Guidelines of care for the management of acne vulgaris." J Am Acad Dermatol 90(5):1006.e1–1006.e30 (2024). PMID 38300170 The American Academy of Dermatology's current clinical guideline, developed by a work group using GRADE methodology. It is the named consensus this rating rests on: it conditionally recommends topical azelaic acid for acne on moderate-certainty evidence from randomised trials, and characterises the agent as comedolytic, antibacterial and anti-inflammatory. Cited for what it is — a treatment recommendation and an evidence grade — and not as a comedogenicity measurement, which it does not contain. A recommendation to use a drug against acne is an efficacy judgement, not a reading of comedogenic potential.
  5. Fitton A, Goa KL. "Azelaic acid. A review of its pharmacological properties and therapeutic efficacy in acne and hyperpigmentary skin disorders." Drugs 41(5):780–798 (1991). PMID 1712709 An independent Adis drug-evaluation review of azelaic acid's pharmacology and clinical use. Cited for identity and mechanism: it describes azelaic acid as a naturally occurring saturated dicarboxylic acid, effective topically (usually as a 20% cream) in comedonal and inflammatory acne and in hyperpigmentary disorders, and it summarises the drug's effect on follicular keratinisation. It is a review, not a new measurement, and it is not a comedogenicity study; it is relied on here at review level for the mechanism and efficacy picture, not for a comedone count of its own.
  6. Katsambas A, Graupe K, Stratigos J. "Clinical studies of 20% azelaic acid cream in the treatment of acne vulgaris. Comparison with vehicle and topical tretinoin." Acta Derm Venereol Suppl (Stockh) 143:35–39 (1989). PMID 2528257 The primary trial report this page's comedone-count claim rests on; abstract read verbatim via EuropePMC, full text not read. It reports a three-month double-blind study of 20% azelaic acid cream against its own vehicle in 92 patients, and a single-blind study in 289 patients with comedonal acne in which azelaic acid was as effective as 0.05% tretinoin cream at reducing comedones and better tolerated. What it establishes: a matched vehicle comparison, so the difference between arms is attributable to the 20% azelaic acid rather than to the base. What it does not: it is a treatment trial in people who already had acne — reduction of existing comedones — not an induction assay on clear skin, and it tests one strength, so it yields no dose–response.
  7. Graupe K, Cunliffe WJ, Gollnick HP, Zaumseil RP. "Efficacy and safety of topical azelaic acid (20 percent cream): an overview of results from European clinical trials and experimental reports." Cutis 57(1 Suppl):20–35 (1996). PMID 8654128 A SECONDARY overview of the same European trial programme, with manufacturer authorship (Zaumseil was with Schering AG, which developed the drug) — disclosed for that reason and weighted as an industry summary rather than as primary data we read. Cited only to show the programme's own account of itself; the comedone-count claim on this page is carried by the Katsambas primary report above, not by this document.
  8. "Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) A recent peer-reviewed clinical review of the comedogenicity field from 1972 onward — a synthesis of the legacy literature, not a new measurement, and independent of Fulton only in authorship. Cited for one field-wide caveat: no standardised comedogenicity test exists, and "non-comedogenic" is an unregulated label. It sets the ceiling on how much any comedogenic number, present or absent, can be asked to carry.
  9. Consumer comedogenic checkers and ingredient databases (CosDNA and similar) Aggregators that publish a 0–5 "acne" number per ingredient with no disclosed method, provenance or citation. Azelaic acid is listed at 0 on scale pages of this kind. Cited as the artefact being corrected, not as a measurement: we traced no primary assay behind that 0, and we make no claim about where it came from or who entered it. It is not carried as our legacy value.

Others in the same family

Actives behave similarly enough that the evidence for one is often wrongly read across to the others. These are its structural relatives, not a guess. What the evidence says about actives as a family ›

Last reviewed 2026-08-05 · How we decide

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