Azelaic acid 20% is a topical dicarboxylic acid used for acne, rosacea, and hyperpigmentation disorders such as melasma and post‑inflammatory hyperpigmentation. It exerts multi‑mechanistic effects: antibacterial against Cutibacterium acnes, anti‑inflammatory via TLR‑2 and ROS pathways, comedolytic/keratinization‑normalizing, and anti‑tyrosinase to reduce excess melanin. Randomized studies show 20% cream improves acne lesion counts and lightens hyperpigmentation over 8–24 weeks, including in darker skin types. It is non‑antibiotic with low risk of bacterial resistance and generally well tolerated, making it suitable for sensitive skin.