What does AHA stand for in skincare chemistry?

AHA stands for alpha hydroxy acid in skincare chemistry.

AHAs are a family of carboxylic acids whose hydroxyl group sits on the carbon next to the acid group. Common examples include glycolic acid, lactic acid, mandelic acid, malic acid, tartaric acid, and citric acid. Their position in the molecule distinguishes them from beta hydroxy acids, such as salicylic acid.

In skincare, AHAs are chemical exfoliants. They weaken the bonds holding surface skin cells together, helping shed accumulated cells and improve the appearance of texture, dullness, and some discoloration. Glycolic acid is generally considered the smallest and most penetration-prone common AHA, while lactic and mandelic acids are also widely used.

A common mix-up is treating AHA as the name of one ingredient. It is a category, not a single molecule. Strength, concentration, formulation pH, and exposure time affect performance and irritation. AHAs can cause redness, flaking, or increased sun sensitivity, so product directions and sun protection matter.