Azelaic acid

Azelaic acid: some good trials for acne, melasma and acne marks, mostly at 15–20% (medicine strength in Korea); limited evidence for redness.

What it is

Azelaic acid is a dicarboxylic acid used on the skin for acne and rosacea. The trials cited below tested it at 15% and 20%. In Korea, products with 15% or more azelaic acid are classified as medicines rather than cosmetics, so cosmetics sold there contain less than the trials used.

Evidence grades by concern

Concern	Grade	Citations
Inflammatory acne	B	King 2023, Reynolds 2024
Acne scarring and marks	B	Shucheng 2024, Kircik 2011
Post-inflammatory hyperpigmentation	B	Shucheng 2024, Passeron 2026
Melasma	B	King 2023, Passeron 2026
Persistent erythema	C	King 2023

Grade A: strong guideline recommendations or Korean MFDS notified actives. B: randomized controlled trials or systematic reviews. C: mechanism, small or uncontrolled studies.

What the evidence shows

Most of the evidence comes from one 2023 systematic review of 43 randomized trials that lasted at least 6 weeks (King 2023), plus two trials on marks left by acne.

Inflammatory acneB

Across 16 acne studies in the review, azelaic acid was more effective than vehicle for overall assessment and acne severity, and 20% azelaic acid reduced more lesions than erythromycin gel, an antibiotic (King 2023). The AAD 2024 acne guideline gives azelaic acid a conditional recommendation, not a strong one (Reynolds 2024).

Acne scarring and marksB

In a 12-week randomized, double-blind, placebo-controlled trial of 72 people with mild-to-moderate acne (60 finished), 15% azelaic acid gel reduced red marks left by acne (post-inflammatory erythema) more than a gel without it did, and the authors reported that it also helped the acne itself (Shucheng 2024). A 16-week pilot study of 15% gel reported improvement in both acne and dark marks, but it had no comparison group and measured change from the start (Kircik 2011).

Post-inflammatory hyperpigmentationB

In the same 12-week trial, dark marks left by acne (post-inflammatory hyperpigmentation) became smaller in both groups, but by week 12 their intensity, size and number had improved significantly more with azelaic acid than with placebo, and the melanin reading of the marks also fell more (Shucheng 2024). The 2026 global consensus on hyperpigmentation lists azelaic acid among topical options for post-inflammatory hyperpigmentation; it does not grade the strength of its recommendations (Passeron 2026). The 16-week pilot study also reported fewer dark marks, but it had no comparison group (Kircik 2011).

MelasmaB

Across seven melasma trials in the review, 20% azelaic acid did significantly better than vehicle for both severity and overall improvement, and better than 2% hydroquinone for overall improvement (King 2023). The 2026 global consensus lists azelaic acid among first-line and maintenance topical options for melasma (Passeron 2026).

Persistent erythemaC

The evidence is limited. Pooling 20 rosacea trials, the review found that after 12 weeks azelaic acid improved the severity of redness (erythema), inflammatory bumps and overall improvement compared with vehicle, and improved redness more than 0.75% metronidazole (King 2023). These trials enrolled people with rosacea, so they do not show what it does for persistent redness from other causes. Our evidence file cites no guideline recommendation for treating redness itself.

What it does not do

The cited trials used 15% or 20% azelaic acid, which in Korea is medicine strength; they do not show how well the lower amounts in cosmetics work. The review found no randomized trials on skin aging. The redness evidence comes from rosacea, and the AAD guideline does not strongly recommend azelaic acid for acne. In the trial on acne marks, dark marks also faded in the placebo group, though less than with azelaic acid.

Safety

Cosmetic Ingredient Review (CIR) Expert Panel conclusion: safe (report year 2012; IJT 31(S1):5-76, dicarboxylic acids group report).