Salicylic acid is a lipophilic monohydroxybenzoic acid, a type of phenolic acid, and a beta hydroxy acid (BHA). It has the formula C7H6O3. This colorless crystalline organic acid is widely used in organic synthesis and functions as a plant hormone. It is derived from the metabolism of salicin. In addition to serving as an important active metabolite of aspirin (acetylsalicylic acid), which acts in part as a prodrug to salicylic acid, it is probably best known for its use as a key ingredient in topical anti-acne products. The salts and esters of salicylic acid are known as salicylates. Salicylic acid is a colorless, crystalline organic carboxylic acid. Salicylic acid is toxic if ingested in large quantities, but in small quantities is used as a food preservative and antiseptic in toothpaste. It is also the key additive in many skin-care products for the treatment of acne, psoriasis, callouses, corns, keratosis pilaris and warts. The carboxyl group (COOH) can react with alcohols, forming several useful esters. The name derives from the latin word for the willow tree (Salix), from whose bark it can be obtained. Salicylic Acid is highly soluble in ethanol, diethyl ether and other polar organic solvents, poorly soluble in water.