Salicylic acid is classified as which type of agent?

• A. Retinoid
• B. Alpha hydroxy acid
• C. Antimicrobial
• D. Beta hydroxy acid

Answer: (D)

This question focuses on how exfoliating acids are classified by the position of the hydroxyl group relative to the carboxyl group. Salicylic acid is structured as 2-hydroxybenzoic acid, meaning the hydroxyl group is on the beta position from the carboxyl group. That makes it a beta hydroxy acid (BHA). BHAs are lipophilic and penetrate oily pores, where they exfoliate inside the pore and help dissolve sebum, making them especially useful for acne-prone skin.

It’s not a retinoid, which are vitamin A derivatives with a different mechanism of action. It isn’t an alpha hydroxy acid, because alpha hydroxy acids have the hydroxyl on the alpha carbon (adjacent to the carboxyl group) and salicylic acid’s hydroxyl is on the beta position. While salicylic acid can have anti-inflammatory effects and may contribute to antimicrobial activity, the classification used in this context is based on its beta-hydroxy structure.