A cosmetic is a chemical formula intended for maintaining and caring for the aesthetic characteristics of the skin without undesirable effects. It consists of natural or synthetic substances for external use on various body parts with the exclusive or main purpose of cleansing, perfuming, changing appearance, or keeping skin in good condition. A drug is intended for use in diagnosing, curing, treating, or preventing disease, or intended to affect the structure or function of the body. Some products can be both cosmetics and drugs, called cosmeceuticals, if they are used for both hygiene and medical treatment purposes.