Frequently Asked Questions
What are alpha hydroxy acids?
Alpha hydroxy acids are a family of water-soluble chemical exfoliants, often derived from sources like sugarcane, milk, and fruit, that help loosen the bonds holding dead skin cells together. By clearing away that buildup, they can improve uneven texture, discoloration, and the appearance of fine lines.
Unlike oil-soluble beta hydroxy acids (BHAs), such as salicylic acid, which can penetrate pores to help clear excess oil and congestion, AHAs primarily work on the skin's surface. And while they all share the same basic job description, some are more aggressive than others. Here's how the most common types stack up, according to Dr. Ruth:
- Glycolic acid: The smallest of the bunch, glycolic acid penetrates skin relatively easily, making it one of the more potent AHAs for tackling rough texture, dark spots, and fine lines. The downside? It can be irritating, especially for sensitive skin.
- Lactic acid: A multitasker that exfoliates while also attracting moisture, making it a good option for dry skin that needs smoothing without sacrificing hydration.
- Mandelic acid: Its larger molecular size means it penetrates more slowly, making it generally better tolerated by sensitive or easily irritated skin.
- Citric, malic, and tartaric acids: These fruit-derived AHAs can contribute to exfoliation and help adjust a formula's pH, though they're less studied as standalone exfoliants.
“Glycolic acid tends to be the most potent exfoliator, while lactic acid can provide exfoliation with some hydrating benefits,” says Dr. Ruth. “Mandelic acid penetrates more gradually and may be better tolerated by easily irritated skin.”
Can you use AHAs with retinol?
Yes, AHAs and retinol can absolutely coexist in your skin-care routine (just look at SkinBetter Science's AlphaRet Exfoliating Peel Pads on our list), but that doesn't mean you should go all in on both at once. Both ingredients encourage skin cell turnover, so combining them can increase the risk of dryness, redness, and irritation, especially if you're new to either one. If you’re a beginner to acids and/or retinol, “rather than layering them in the same routine, I recommend alternating nights,” says Dr. Ruth. “For example, using an AHA one night and separate retinol another. You will get the benefits of both while giving the skin barrier time to recover.”
Who shouldn’t use AHAs?
AHAs aren't off-limits for sensitive skin, but if you're dealing with an active eczema flare, rosacea, a compromised skin barrier, or skin that's already irritated or peeling, it's best to hold off until things calm down. The same goes for freshly waxed skin or skin recovering from certain in-office treatments, like lasers and chemical peels. Even if your skin generally tolerates exfoliation well, dermatologists warn that AHAs can increase sun sensitivity, making your skin more vulnerable to UV damage. When introducing an AHA, start slowly, consider using it at night, and be especially diligent about applying broad-spectrum sunscreen with SPF 30 or higher during the day.
Meet the experts
- Alexandra Bowles, DO, a board-certified dermatologist at MONA Dermatology based in Cincinnati
- Nicole Ruth, MD, a board-certified dermatologist at Weiser Skin MD based in New York City
- Mamina Turegano, MD, a board-certified dermatologist, internist, and dermatopathologist based in New Orleans
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