Az
Azelaic Acid
Azelaic AcidActive
An acid used for acne, redness and dark spots. Sold over the counter and, at higher strengths, by prescription.
What it does
It’s an acid made by yeast that lives on skin. It fights acne bacteria and fades dark spots. Its redness results come from prescription strengths, in rosacea with bumps. Over-the-counter products are usually 10%; prescription ones are 15–20%.
The evidence, graded
expert consensusFine together. Both reviews call azelaic acid well tolerated; neither used it with a retinoid, and nothing Drop has read shows it calming retinoid irritation.Sieber 2014 · Skin Pharmacology and Physiology ↗
expert consensusHydroquinone is absorbed through skin at 35–45% — much higher than most topicals. Pregnancy and breastfeeding guidance is to avoid it, even though existing studies have not shown harm.Bozzo 2011 · Canadian Family Physician ↗
expert consensusPrescription labels give two numbers. On the 20% cream, most people with inflamed acne improved within four weeks. The 15% rosacea gel says to check back if nothing has improved after 12 weeks, the length of its trials. Reviews find azelaic acid effective for acne and for melasma, where trials ran 8 to 24 weeks, and well tolerated. These are prescription products; no source Drop has read times an over-the-counter 10% product.Sieber 2014 · Skin Pharmacology and Physiology ↗
moderateIn a 1989 study in Berlin of 47 people (12 with normal skin, 15 with oily skin and 20 with acne), a 20% azelaic acid cream improved acne but made no visible change to normal or oily skin. It didn't change how much oil skin made, what the oil was made of, or the size of the oil glands.Mayer-da-Silva 1989 · Acta Dermato-Venereologica Supplementum ↗
Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.
Pairs worth knowing
Browse all 1238 ingredients — grouped by what they do, each with whatever evidence we can cite.
This page is public so a shared ingredient card always has its sources behind it — and so you can check them without an account.
Want more like this?
Every evidence-based flag cites its source, Drop tells you when your routine is complete, and it helps you simplify — instead of selling you more. The app launches on iOS and Android in October 2026. Rate my routine works today at /rate — no sign-in.