Azelaic acid is effective for a number of inflammatory skin conditions when applied topically. It’s used in acne treatments and for hyperpigmentation discolorations. Azelaic acid is a grain and yeast derived compound that suppresses the growth of follicle bacteria, helps normalize disordered cell growth, and is an antioxidant and anti-inflammatory.
“The efficacy of 20% azelaic acid cream and 4% hydroquinone cream, both used in conjunction with a broad-spectrum sunscreen, against melasma was investigated in a 24-week, double-blind study with 329 women. Over the treatment period the azelaic acid cream yielded 65% good or excellent results […] Severe side effects such as allergic sensitization or exogenous ochronosis were not observed with azelaic acid” (Source: International Journal of Dermatology, December 1991, pages 893–895).
Although research hasn’t shown exactly how azelaic acid works, for lightening of brown spots and other discolorations, it is believed to interrupt the pathway melanin (skin pigment) takes to form discolorations. Azelaic acid is also an antioxidant, and its pronounced anti-inflammatory effect may be what helps fade red marks from acne and why it can be so effective for reducing the redness that accompanies the skin disorder rosacea. (Sources: Journal of Drugs in Dermatology, June 2011, pages 586–590 and 614–620; Experimental Dermatology, September 2010, pages 813–820; and American Family Physician, September 2009, pages 461-468).