# Lactic vs glycolic vs mandelic acid for sensitive skin
Source: https://theconstantbeauty.com/compare/lactic-vs-glycolic-vs-mandelic-acid-for-sensitive-skin/
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Publisher: The Constant (theconstantbeauty.com). Cite as "The Constant".
Generated: 2026-09-16T18:24Z
**Compares:** Lactic acid vs Glycolic acid
**Criteria:** Molecule size, Penetration and speed, Extra properties, Irritation potential, Typical leave-on range, Sun sensitivity, Safety assessments (to our understanding)
## Context for the verdict
Choose glycolic acid if your skin is resilient, you want the fastest visible change in texture, and you can build up from a low percentage. Start at 5% or less, two or three evenings a week, before going daily.
Choose lactic acid if your skin is dry as well as sensitive, or if glycolic acid has left it tight. It exfoliates more gently and adds moisture rather than taking it away.
Choose mandelic acid if your skin is reactive, redness-prone, or has a deeper tone that darkens easily after irritation. Its slow, even action is the most forgiving of the three, and it is a reasonable first AHA for anyone who has never used one.
None of the three is right for everyone. Whichever you pick, the percentage, the pH of the formula and how often you use it matter more than the name of the acid.
## Comparison
Lactic, glycolic and mandelic acid are all alpha hydroxy acids (AHAs). Each loosens the bonds between dead surface cells so they shed more evenly, which is what makes skin look smoother and brighter after a few weeks of use. For sensitive skin the differences that matter come down to molecule size, how quickly each acid moves into the skin, and what else it does while it is there.
Glycolic acid is the smallest of the three, at about 76 g/mol, so it penetrates fastest and works quickest. That speed is also why it is the most likely to sting, flush or over-exfoliate reactive skin, especially at higher percentages or lower pH.
Lactic acid is a little larger, about 90 g/mol, and moves more slowly. It is also a natural component of the skin’s own moisturising system, and at low concentrations it behaves as a humectant as well as an exfoliant. For dry, sensitive skin that still wants gentle resurfacing, that dual role is useful.
Mandelic acid is the largest, about 152 g/mol, and more oil-soluble than the other two. It penetrates slowly and evenly, which spreads its action out and lowers the chance of a sudden irritation response. It is widely described as the gentlest of the three for this reason, though it has far fewer published studies behind it than glycolic acid.
All three increase the skin’s sensitivity to UV while in use. Daily broad-spectrum sunscreen is not optional with any of them, and a patch test before the first full application is sensible for anyone who reacts easily.
## References
1. Tang SC, Yang JH. Dual effects of alpha-hydroxy acids on the skin. Molecules. 2018;23(4):863.
2. Kornhauser A, Coelho SG, Hearing VJ. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clin Cosmet Investig Dermatol. 2010;3:135–142.
3. Cosmetic Ingredient Review Expert Panel. Final report on the safety assessment of glycolic acid, lactic acid, their salts and esters. Int J Toxicol. 1998;17(Suppl 1):1–241.
4. PubChem compound summaries: glycolic acid (CID 757), lactic acid (CID 612), mandelic acid (CID 1292). National Library of Medicine.