What lactic acid is

Lactic acid is an alpha hydroxy acid (AHA), a common AHA in cosmetic products. In an AHA product used for exfoliation, the intended effect is shedding of surface skin. That description does not tell you how much exfoliation to expect from an individual bottle: the extent depends on the AHA type and concentration, the product pH, and other ingredients. An ingredient list may identify lactic acid without disclosing the final pH or showing that the acid is present at an exfoliating concentration. Glycolic acid is another common AHA, not an alternative name for lactic acid; neither is universally gentler in every formula.

Reading the formula and its claims

AHA cosmetics may be marketed for improved-looking texture and tone, but that does not establish the result of every lactic-acid formula. It also notes that AHAs can serve other purposes in cosmetics, including adjustment of acidity; its statement concerns AHAs as a class and does not prove the specific role of lactic acid in a particular formula. Read the stated use of the finished product rather than treating an INCI name as a performance test. The same ingredient can appear in products with different concentrations, pH values, instructions and contact times. These differences matter especially when comparing a leave-on consumer product with a professionally applied, briefly used and thoroughly rinsed peel.

Sun exposure and the limits of safety assessments

Follow the label and use sunscreen and protective clothing, limiting sun exposure during AHA use and for a week afterward. Findings about AHA creams and UV sensitivity do not quantify the risk for every lactic-acid product. A safety assessment for consumer cosmetic products containing lactic or glycolic acid used these conditions: AHA at no more than 10%, final pH at least 3.5, plus a formula that avoids increased sun sensitivity or directions for daily sun protection. Professional salon use at up to 30% and pH at least 3.0 has different conditions: brief application, thorough rinsing, trained operators and sun-protection directions. Neither context is a blanket clearance for arbitrary high-strength home peels. For label terminology, see broad-spectrum sunscreen.

Cosmetic versus therapeutic use

Under US law, intended use and claims can change a product’s category. In the US, AHA products intended to treat acne or lighten skin may be regulated as drugs. Merely finding lactic acid on an ingredient list does not classify a product as a drug, nor does a cosmetic exfoliation claim demonstrate treatment of a disease. The practical distinction is between what a finished product says it is intended to do and what has actually been tested; ingredient safety conditions do not establish clinical efficacy for a particular retail product.