Do I need sunscreen with glycolic acid?

Yes. AHAs make skin more sensitive to sun, so daily sunscreen is part of using them. Skipping it undoes the look you are working toward and leaves skin more exposed.

What percentage of glycolic acid should I start with?

Lower concentrations, roughly 5 to 8%, used a few nights a week is a common starting point, building up to more frequent use as skin adjusts.

Can glycolic acid be layered with vitamin C?

They can share a routine, but both are low pH actives, so stacking them in the same layer raises the chance of visible irritation. Many people use one in the morning and the other at night, or alternate days.

Alpha hydroxy acid (AHA)

Glycolic Acid

INCI: Glycolic Acid·Studied at 5–10% (leave-on)·Strong evidence

The smallest alpha hydroxy acid and the most-studied surface exfoliant, associated with the appearance of a smoother texture, brighter even tone and softened fine lines. Its small molecular size lets it move into the surface layers of skin efficiently, which is part of why it has the deepest clinical record of any AHA and shows up across toners, serums and in-office peels alike. Results are cumulative; most of the published research looks at weeks to months of regular use rather than a single application.

Studied for

·The appearance of a smoother, more even surface
·The look of brighter, more even tone
·The appearance of softened fine lines
·The look of more refined-looking pores with continued use

How it’s thought to work

Loosens the bonds between surface skin cells and is studied for association with the look of a fresher, more even surface; low pH drives it and it raises sun sensitivity, so daytime sunscreen matters. With continued use it is also studied for supporting the appearance of firmer-looking skin, tied to encouraging steadier surface cell turnover. Higher concentrations and in-office peel strengths are studied for a more pronounced version of the same effect, at the cost of more visible downtime.

Landmark study

Topical glycolic acid was linked to a smoother, more evenly toned looking appearance in sun exposed skin in a small clinical study.

Improving the cosmetic appearance of photoaged skin with glycolic acid. Journal of the American Academy of Dermatology, 1997.

View on PubMed (PMID 9204071) ↗

Layering note

Often kept apart from: retinoids in the same layer for sensitive skin.

Questions

Do I need sunscreen with glycolic acid?: Yes. AHAs make skin more sensitive to sun, so daily sunscreen is part of using them. Skipping it undoes the look you are working toward and leaves skin more exposed.
What percentage of glycolic acid should I start with?: Lower concentrations, roughly 5 to 8%, used a few nights a week is a common starting point, building up to more frequent use as skin adjusts.
Can glycolic acid be layered with vitamin C?: They can share a routine, but both are low pH actives, so stacking them in the same layer raises the chance of visible irritation. Many people use one in the morning and the other at night, or alternate days.

Serums we’ve scored with Glycolic Acid

References

This dossier covers the efficacy evidence. For the safety and concern profile of Glycolic Acid, see PlainBody ↗, our sister site.