Does azelaic acid act only on Acne vulgaris or on other forms as well?

Azelaic acid is not limited to Acne vulgaris. Studies indicate it is also effective on other forms, for example hidradenitis suppurativa (Acne inversa). Effectiveness depends on the concentration of azelaic acid in the product. For cosmetic products a concentration up to roughly 14% is generally used, while pharmaceutical products are based on 20%.