Azelaic Acid — the only ingredient that treats acne, fades hyperpigmentation and is safe during pregnancy
Azelaic acid 15-20% (Rx) vs 10% (OTC): inhibits tyrosinase, fights C. acnes and is Pregnancy Category B. Compared with hydroquinone and retinoids.
In dermatology there are few players that can simultaneously fight acne, reduce hyperpigmentation and pose no threat to pregnant women. Azelaic acid — listed on the INCI as Azelaic Acid — is one of them. It occurs naturally in the grains of wheat, rye and barley, and in human skin it is produced by the yeast Malassezia furfur. Although known since the 1970s, it was only the past decade that brought it the recognition it deserves beyond the dermatologist's office.
Concentrations: prescription vs drugstore shelves
The dividing line between a therapeutic preparation and a cosmetic runs along concentration:
- 15–20% (Rx) — available by prescription. Skinoren (Bayer), in the form of a 20% cream or a 15% gel, is the gold standard in treating acne vulgaris and rosacea. In Poland it is available on prescription and reimbursed for selected indications.
- 10% (OTC) — cosmetic products available without a prescription, offered by brands such as The Ordinary, Paula's Choice and Geek & Gorgeous. Regulation (EC) No 1223/2009 does not set a separate limit for azelaic acid — national pharmaceutical authorities decide where the line between a cosmetic and a medicine falls.
- Below 5% — no convincing evidence of clinical efficacy. If azelaic acid appears at the end of the INCI list, it most likely serves a pH-buffering function rather than a therapeutic one.
Mechanism I: tyrosinase inhibition — tackling hyperpigmentation
Azelaic acid blocks the enzyme tyrosinase — the catalyst for the first two steps in the melanin synthesis pathway. Importantly, it acts selectively: it inhibits overactive melanocytes (responsible for hyperpigmentation) more strongly than normally functioning ones. This is a fundamental difference compared with hydroquinone, which affects all melanocytes indiscriminately, carrying a risk of depigmentation (leukoderma).
A study by Balina and Kligman (1981) in the British Journal of Dermatology showed that 20% azelaic acid applied twice daily for 6 months reduced the intensity of melasma comparably to 2% hydroquinone — without rebound effects (darkening of the skin after discontinuation) and without the risk of cytotoxicity towards melanocytes.
Comparison with hydroquinone — safety profile
| Parameter | Azelaic acid 20% | Hydroquinone 2–4% |
|---|---|---|
| Selectivity towards melanocytes | Yes (acts on overactive ones) | No (acts on all) |
| Risk of ochronosis | None | Yes (with long-term use) |
| Safety during pregnancy | Category B (FDA) | Category C (FDA) |
| Maximum duration of use | No limit | 3–5 months (breaks mandatory) |
| Regulation in the EU | Permitted in cosmetics | Banned in cosmetics since 2001 (Annex II, entry 1339) |
It is worth stressing: hydroquinone is banned in cosmetic products in the European Union as of 2001 under Directive 76/768/EEC (now Regulation 1223/2009, Annex II). It is available solely as a prescription medicine. Azelaic acid is not subject to this restriction.
Mechanism II: antibacterial action against Cutibacterium acnes
Formerly classified as Propionibacterium acnes and renamed in 2016 to Cutibacterium acnes, this gram-positive bacterium is the main player in the pathogenesis of inflammatory acne. Azelaic acid acts on it in two ways:
- It inhibits the synthesis of bacterial proteins by disrupting the thioredoxin pathway.
- It normalises keratinisation of the hair-follicle openings, hindering the formation of microcomedones — the first stage of acne lesions.
Unlike antibiotics (erythromycin, clindamycin), azelaic acid does not generate bacterial resistance — it can be used long-term without the risk of selecting resistant strains. This is a key advantage in an era of rising antibiotic resistance.
Category B during pregnancy — what does it mean in practice?
The FDA (Food and Drug Administration) classification divides medicines into pregnancy safety categories from A to X. Category B means: "animal studies have not shown a risk to the foetus and there are no controlled studies in pregnant women, OR animal studies have shown an adverse effect that controlled studies in humans have not confirmed."
Azelaic acid is one of the few active ingredients used in dermatology that has retained Category B. For comparison:
- Retinoids (tretinoin, adapalene, tazarotene) — Category X (absolutely contraindicated).
- Salicylic acid (BHA) — Category C (warning; systemic use contraindicated).
- Benzoyl peroxide — Category C.
- Niacinamide — no FDA classification (limited data).
This makes azelaic acid a first-choice ingredient for treating acne and hyperpigmentation in pregnant women, alongside glycolic acid (Category B at low concentrations) and lactic acid.
How to use azelaic acid in your daily routine?
Apply OTC preparations (10%) in the evening on cleansed skin, before your moisturiser. SPF is mandatory in the morning — although azelaic acid does not increase photosensitivity the way retinoids do, sun protection is standard with any pigmentation therapy.
Azelaic acid combines safely with most active ingredients — niacinamide, hyaluronic acid, ceramides. Caution is advised only when used at the same time as strong exfoliants (AHA above 10%, BHA above 2%), where the risk of irritation adds up.
Before you choose a product, compare formulas in our ranking of face creams — you'll see which preparations contain azelaic acid at an effective concentration and which merely list it at the bottom of the INCI list. Also check the PurScore ingredient database to learn how it interacts with other active substances in your cosmetic.
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FAQ
Yes, although results appear more slowly than with the 20% (Rx) concentration. Clinical studies have shown a visible reduction in melasma after 12-16 weeks of using a 10% preparation twice daily. If you see no improvement after 4 months, it's worth consulting a dermatologist about a prescription preparation.
Yes — it's one of the more effective combinations in dermatology. Azelaic acid (in the morning) + a retinoid (in the evening) creates synergy: azelaic acid inhibits melanogenesis and C. acnes, while the retinoid accelerates cell turnover. Don't use them together in the same application, to avoid irritation.
Azelaic acid is FDA Pregnancy Category B — one of the safest among active dermatological ingredients. It is recommended as a first-choice treatment for acne and hyperpigmentation in pregnant women, unlike retinoids (Category X — absolutely prohibited) or salicylic acid (Category C).
Azelaic acid acts selectively on overactive melanocytes without damaging normal ones. Hydroquinone inhibits all melanocytes, which risks depigmentation and, with long-term use, ochronosis (irreversible grey-blue discolouration). On top of that, hydroquinone has been banned in cosmetics in the EU since 2001.
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