What Does Alpha Hydroxy Acid Do? | Skin Science Explained

Alpha hydroxy acids exfoliate skin by dissolving dead cells, smoothing fine lines, improving texture, and helping unclog pores.

For the full breakdown, see our best Alpha Hydroxy Body Wash guide.

Alpha hydroxy acids—often shortened to AHAs—are among the most common active ingredients in skincare. They appear in cleansers, lotions, creams, toners, and facial peels, and the science behind them is straightforward: these acids gently dissolve the bonds holding dead skin cells to the surface, revealing fresher skin underneath. Whether you’re chasing a smoother texture, brighter tone, or clearer pores, AHAs are doing the heavy lifting.

How Alpha Hydroxy Acids Work On Your Skin

AHAs work through chemical exfoliation. Instead of the abrasive scrubbing of a physical exfoliant, the acid loosens the “glue” between dead skin cells on the surface, allowing them to slough away naturally. This process is why your skin feels noticeably smoother after just one or two uses.

That exfoliation is the root of every benefit the ingredient is known for:

• Softening fine lines and surface wrinkles
• Improving overall skin texture and tone
• Unclogging pores by clearing the dead-cell buildup around them
• Improving overall skin condition and radiance

Some formulations are also marketed for acne, the appearance of scars, and discoloration. In certain products, AHAs serve a second role as pH adjusters, helping other ingredients function properly.

Are Alpha Hydroxy Acids Safe? What The FDA Says

The safety of AHAs in cosmetics comes down to two numbers: concentration and pH. The U.S. Food and Drug Administration’s guidance, based on the Cosmetic Ingredient Review panel’s findings, considers glycolic acid and lactic acid safe in cosmetic products at concentrations of 10% or less, provided the final formula has a pH of 3.5 or greater.

In plain terms, a product meeting those thresholds has cleared the safety bar for consumer use. Products with higher concentrations exist—mostly in professional peels—but they are not cosmetic products in the FDA’s view.

This guidance applies to cosmetics on the US market and does not establish that AHAs treat medical conditions. Some products are marketed that way, but the FDA’s safety finding is about cosmetic use, not medical efficacy.

Side Effects: What To Expect And Who Should Be Careful

AHAs are not risk-free. The most common side effects include temporary irritation, burning, redness, itching, swelling, dryness, and flaking. People with sensitive skin should start gently, and those with broken or sunburned skin should wait for it to heal before starting any AHA product.

There is one caveat that matters more than the others: sun sensitivity. The FDA notes that topical AHA products may increase your skin’s sensitivity to the sun while you’re using them—and for up to a week after you stop. Daily sunscreen while using an AHA product is a requirement, not a suggestion.

For most people, patch testing on a small area before full application is the smart first step. If irritation appears, stop use entirely. Avoid stacking an AHA with other aggressive treatments to keep your skin barrier intact.

Always follow the product’s own directions, and if a formula promises sun-protection measures, follow them as labeled.

Choosing A Product: What Actually Matters

When you pick an AHA product, the ingredient list tells the real story. Check for glycolic acid or lactic acid—the two molecules the safety data covers—and confirm the concentration sits at 10% or below for at-home use.

Start slowly. A few nights a week is plenty for most skin types. Pair your AHA with sun protection every single morning, and you have the full formula for smoother, clearer skin without the irritation risk.