Alitretinoin is a retinoid, related to vitamin A. Alitretinoin affects the growth and development of skin cells. Alitretinoin topical (for the skin) is used to treat skin lesions caused by AIDS-related Kaposi’s sarcoma. Do not shower or swim until at least three (3) hours after application of alitretinoin gel. Common side effects include rash, warmth or slight stinging of the skin, and lightening or darkening of the skin.