Polyhydroxy Acids (PHA)

Polyhydroxy Acids (PHA) — a group of exfoliating acids, including gluconolactone and lactobionic acid, that work similarly to AHAs but have larger molecules for a gentler effect. Their size limits how deeply and quickly they penetrate, which makes them a popular choice for sensitive skin. Many also provide humectant and antioxidant benefits alongside exfoliation.

Key points

• PHAs such as gluconolactone and lactobionic acid have larger molecules than traditional AHAs, resulting in gentler, slower exfoliation.
• Their reduced penetration makes them well suited to sensitive, reactive, or easily irritated skin.
• Several PHAs also act as humectants, helping the skin attract and retain moisture.
• Some, like lactobionic acid, offer antioxidant properties in addition to exfoliation.
• They are often described as causing less sun sensitivity than stronger acids, though sunscreen remains advisable.

Frequently asked

How are PHAs different from AHAs?

PHAs work like AHAs to exfoliate the surface but have larger molecules that penetrate more slowly, generally making them gentler and better tolerated by sensitive skin. Many also add hydration and antioxidant benefits.

Are PHAs a good starting exfoliant?

They are often recommended for beginners and sensitive skin because of their mildness and added moisturizing qualities. Consistent use is still needed to see improvements in texture and radiance.

Related topics

• Vitamin C in Skincare
• Retinol: The Complete Guide
• Vitamin F (Essential Fatty Acids)
• PHA (Polyhydroxy Acid)
• Fatty Acids in Skincare
• Amino Acids in Skincare
• Retinoids + Exfoliating Acids Timing
• PHA vs AHA

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