Salicylic acid: A substance obtained from plants (white willow back and wintergreen leaves) and also synthesized which is versatile and possesses bacteriostatic, fungicidal, and keratolytic actions.

Salicylic acid is used as a food preservative and as an antiseptic in toothpaste. It is a peeling agent in ointments, creams, gels, and shampoos applied to reduce the scaling of the skin or scalp in psoriasis. It is the active ingredient in many skin products for the treatment of acne since it causes skin cells to slough off more readily, preventing them from clogging up the pores. Salicylic acid reacts with acetic acid to acetylsalicylic acid, better known as aspirin.

Salicylic acid is also chemically known as orthohydroxybenzoic acid.