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.