What is Salicylic acid?

Salicylic acid is a beta-hydroxy acid derived from the bark of a willow tree. It occurs naturally in various plants
including, but not limited to, black cohosh, blue flag, American pennyroyal, cassie, coca, dog’s grass, glory lily,  marigold, seal island cotton, plantain, rue, wintergreen, ylang yland and willow bark. As Salicylic Acid and its salts  and esters have many functions, these ingredients may be used in many types of cosmetics and personal care products  including moisturizers, skin cleansing products, shampoos, as well as skin care, hair care, suntan and sunscreen  products, as well as in mouthwashes and dentifrices. 
The safety of salicylic acid used as a cosmetic ingredient has been evaluated by both the cosmetic industry and FDA. At a meeting in February 2000, the Cosmetic Ingredient Review (CIR) Expert Panel, the cosmetic industry's independent body for reviewing the safety of cosmetic ingredients, reached the tentative conclusion that the use of salicylic acid related substances in cosmetics is "safe as used when formulated to avoid irritation and when formulated to avoid increased sun sensitivity."