Azelaic Acid
Azelaic acid is a carboxylic acid (not an AHA or BHA) that occurs naturally in wheat, rye, and barley. It is used in cosmetic and pharmaceutical formulations at concentrations ranging from 5% to 20%. In the US it is classified as a prescription drug, while in the EU it can be purchased freely at concentrations up to 10%.
Azelaic acid has demonstrated antibacterial activity against acne-causing Propionibacterium acnes, making it effective for acne treatment at 20% (comparable to 0.05% retinoic acid, 5% benzoyl peroxide, and 2% erythromycin). It also regulates skin cell production in pores to reduce blackheads and whiteheads, exerts a proven anti-inflammatory effect useful for rosacea (standard prescription dose: 15%), and provides skin-lightening properties shown to be comparable to 2–4% hydroquinone for post-inflammatory hyperpigmentation and melasma.
Prescription-strength concentrations (15% for rosacea, 20% for acne) require medical supervision in the US. Effectiveness for solar lentigines (age spots) appears limited based on cited studies. Individuals with sensitive skin should introduce it gradually, particularly at higher concentrations.
