Glycolic Acid

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What Is Glycolic Acid in Skincare?

Glycolic acid is the smallest alpha hydroxy acid (AHA), a water-soluble fruit and sugar acid that loosens the bonds holding dead surface cells together so they shed more evenly. In skincare it is used as a chemical exfoliant that leaves skin looking smoother, brighter, and more even in tone. Its small molecular size is why it works quickly, and also why the concentration and pH of a product matter so much.

EWG Skin Deep score for glycolic acid EWG Skin Deep rating for glycolic acid

Glycolic Acid Quick Facts

Property Details
INCI name Glycolic Acid
Common names Hydroxyacetic acid, AHA, fruit acid
Source Originally isolated from sugar cane; most cosmetic glycolic acid today is made synthetically for purity and consistency
Form White crystalline powder (99%) or clear liquid solution (commonly 70%)
Solubility Water soluble
Typical usage rate Supplier range 0.1-6.0% for 99% glycolic acid and 0.5-8.5% for the 70% solution (Spec-Chem catalogue, supplier data). For leave-on retail products, the Cosmetic Ingredient Review (CIR) safety limit is 10% or less
pH range Final product pH 3.5 or higher for retail products (CIR). Glycolic acid has a pKa of about 3.8, so lower pH means more free acid and a stronger effect
Skin types Normal, oily, combination, dull or uneven-looking, mature skin. Dry and sensitive skin should start low

How Glycolic Acid Works on the Skin

The outer layer of skin is made of flattened cells held together by a kind of mortar. As skin ages, those cells hang on longer, which makes the surface look dull and rough and makes fine lines look deeper. Glycolic acid weakens the attachments between these surface cells, so they release more uniformly. The result people notice is a smoother feel, more light reflection (glow), and a more even look to tone and texture.

In a pilot study by Ditre and colleagues (1996), adults applied a 25% AHA lotion (glycolic, lactic, or citric acid) to one forearm and a placebo lotion to the other for an average of six months. Skin thickness on the AHA forearms increased by about 25%, and biopsies measured a thicker epidermis, more acid mucopolysaccharides, better elastic fiber quality, and higher collagen density in the upper dermis. That was a high concentration used on the forearm under study conditions; retail facial products are limited to 10% or less.

Because it removes part of the surface layer, glycolic acid also makes skin more sensitive to the sun. The FDA reports that in a study of AHA use, sensitivity to UV-induced reddening rose by 18% after four weeks of application, and the effect went away within a week of stopping. Daily sunscreen is not optional when you use AHAs.

How to Use Glycolic Acid

  • Start slowly. Use a glycolic product two or three evenings a week, then build to nightly if your skin stays comfortable.
  • Apply to clean, dry skin. Damp skin can increase penetration and tingling.
  • Follow with a moisturizer and, in the morning, a broad-spectrum sunscreen. Continue sunscreen for a week after you stop using AHAs.
  • Do not stack strong actives on the same night. Alternate glycolic acid with retinol or high-strength vitamin C rather than layering them.
  • Peels above 10% belong with a licensed professional.

Formulating Notes

  • Add glycolic acid to the water phase of a formula after any emulsion has cooled below 40°C (104°F).
  • Adjust and confirm final pH with a calibrated meter. A pH of 3.5-4.0 is the working range for a leave-on retail product.
  • Many thickeners (carbomer in particular) lose viscosity at low pH. Choose acid-tolerant gums such as xanthan or hydroxyethylcellulose, or acid-stable emulsifiers.
  • Check that your preservative works at a low pH. Store in an opaque, airtight bottle away from heat.

Who Glycolic Acid Suits

Glycolic acid is a good fit for normal, oily, and combination skin, and for mature skin that looks dull, rough, or uneven. Because it is the most penetrating AHA, people with dry or sensitive skin often do better with the larger, gentler lactic acid. If you have sensitive skin, patch test first (inner arm, 24 hours) and start at the lowest rate in the range, then work up.

Frequently Asked Questions

What does glycolic acid do for your skin?

Glycolic acid loosens the bonds between dead surface cells so they shed evenly. Skin looks smoother, brighter, and more even in tone with regular use.

How often should I use glycolic acid?

Start two or three evenings a week. If your skin stays comfortable after two to three weeks, you can build up to nightly use of a 5-10% product.

Can I use glycolic acid every day?

Many people can once their skin adjusts, especially at 5-10%. Lasting stinging, peeling, or redness means you should cut back.

What is the difference between glycolic acid and salicylic acid?

Glycolic acid is a water-soluble AHA that works on the skin's surface for smoothness and glow. Salicylic acid is an oil-soluble beta hydroxy acid that works inside oily pores. See glycolic vs salicylic acid for a side-by-side comparison.

Can I use glycolic acid with retinol?

Yes, but not usually in the same application. Alternate nights so each has a chance to work without overloading the skin.

Can I use glycolic acid with vitamin C or niacinamide?

Niacinamide pairs well with glycolic acid. Use low-pH vitamin C at a different time of day, such as vitamin C in the morning and glycolic acid at night.

Why does glycolic acid tingle?

A brief tingle is common because of the low pH. A burning feeling that does not fade within a minute or two means the product is too strong for your skin right now.

Does glycolic acid make you sensitive to the sun?

Yes. The FDA reports sensitivity to UV-induced reddening rose 18% after four weeks of AHA use. Wear broad-spectrum sunscreen daily and for a week after you stop.

Shop Glycolic Acid Products

Prep freshly exfoliated skin with the Watermelon Brightening Tonic Facial Mist from this collection, and explore our full range of alpha hydroxy acid products. For a full how-to on at-home peels, read Glycolic Acid Peels at Home: A Complete How-To Guide.

Sources

  • Ditre CM, Griffin TD, Murphy GF, et al. Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study. J Am Acad Dermatol. 1996;34(2 Pt 1):187-195. doi:10.1016/s0190-9622(96)80110-1
  • U.S. Food and Drug Administration. Alpha Hydroxy Acids (CIR safety conclusions and sunburn alert).
  • Kornhauser A, Coelho SG, Hearing VJ. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clin Cosmet Investig Dermatol. 2010;3:135-142. doi:10.2147/CCID.S9042
  • Spec-Chem, Ingredients Catalogue 2026 V1, SpecWhite PLGA99 and PLGA70 glycolic acid (supplier data).

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

About the Author
Written by Kari Thomas, cosmetic formulator and founder of Skin Perfection.