Glossary

AHA (Alpha Hydroxy Acid)

Written by Reviewed by the SYNC editorial team Published Last reviewed Editorial standards

AHA (Alpha Hydroxy Acid) — a group of water-soluble acids used in skincare to exfoliate the surface of the skin by loosening the bonds between dead skin cells. Common examples include glycolic and lactic acid, which are often used to improve texture, tone, and the appearance of dullness.

Key points

  • AHAs are water-soluble, so they primarily work on the skin's surface rather than deep within pores.
  • Glycolic acid is one of the smallest AHA molecules, while lactic acid is often considered gentler and more hydrating.
  • Regular use can help improve the look of uneven texture, fine lines, and dull or discolored skin over time.
  • AHAs can increase sun sensitivity, so daily sunscreen use is generally recommended alongside them.

Frequently asked

What is the difference between AHAs and BHAs?

AHAs are water-soluble and mainly exfoliate the skin's surface, while BHAs are oil-soluble and can penetrate into pores. AHAs are often favored for texture and tone, and BHAs for oily or congested skin.

Do AHAs make skin more sensitive to the sun?

Yes, AHAs can increase the skin's sensitivity to UV light, both during use and for a period afterward. Applying broad-spectrum sunscreen daily is generally recommended.

Related topics

This is a foundational entry in the SYNC Skin Encyclopedia and is expanded over time. Educational information only — not medical advice.

Encyclopedia

Further reading

This entry was written and checked against the sources below. They are published by clinical and scientific bodies, they are listed most readable first, and each one opens in a new tab. They are background for the whole entry rather than footnotes to individual sentences.

  1. Chemical peels (face peels) DermNet NZ Clinical guidance dermnetnz.org
  2. Cosmetics Alpha Hydroxy Acids U.S. FDA Regulatory and safety fda.gov
  3. Guidance for Industry: Labeling for Cosmetics Containing Alpha Hydroxy Acids U.S. FDA Regulatory and safety fda.gov
  4. Evaluating the Efficacy and Safety of Alpha-Hydroxy Acids in Dermatological Practice: A Comprehensive Clinical and Legal Review PubMed Central Peer-reviewed, open access pmc.ncbi.nlm.nih.gov
  5. Cosmetic and dermatologic use of alpha hydroxy acids PubMed Peer-reviewed (abstract) pubmed.ncbi.nlm.nih.gov
  6. Evaluating the Efficacy and Safety of Alpha-Hydroxy Acids in Dermatological Practice: A Comprehensive Clinical and Legal Review PubMed Peer-reviewed (abstract) pubmed.ncbi.nlm.nih.gov

SYNC does not publish medical advice. Nothing here replaces a consultation with a doctor or a pharmacist about your own skin.