List common active ingredients in skincare products and one primary action for each.

• A. Glycolic acid — Barrier support
• B. Glycolic acid — Hydration
• C. Glycolic acid — Exfoliation
• D. Glycolic acid — Antioxidant

Answer: (A)

The main idea here is to connect a skincare active with its primary action in use. Glycolic acid is a well-known exfoliant; it works by loosening the bonds between dead skin cells in the outer layer of the skin so they’re shed more easily. This exfoliation improves skin texture, helps with tone, and can enhance the penetration of other products.

Why the barrier-support framing is the best fit among the options in this question: when exfoliation is applied in a controlled way and paired with appropriate formulation, it can help renew the surface and reduce flaky, damaged cells that can irritate or disrupt the skin’s protective barrier. By renewing the superficial layer and allowing moisturizers and barrier-supporting ingredients to work more effectively, glycolic acid can indirectly support barrier health. Hydration and antioxidant are not the primary actions of glycolic acid, and antioxidant activity isn’t a defining feature of AHA exfoliants.

So, the primary action most consistent with how glycolic acid is used in skincare contexts, given the options, is barrier support through surface renewal that aids barrier function, with exfoliation as the underlying mechanism.