Retin-A (tretinoin) is a form of vitamin A which is used to treat acne and improving the skin?s health and appearance. Tretinoin belongs to a class of drugs called retinoids. Acne often develops in teenagers and young adults due to hormonal changes which leave acne scars and blemishes. Acne pimples mostly occur on the face, neck and back. Adolescents are often conscious about their appearance and stubborn acne may ravage their skin in a very young age.