Lactic Acid vs Glycolic Acid
Two alpha hydroxy acids that both smooth and brighten — but one is gentler and hydrating, the other stronger and deeper. Here's which AHA matches your skin.
Lactic and glycolic acid are the two most common alpha hydroxy acids (AHAs), and they do the same broad job — dissolving the bonds between dull surface cells to reveal smoother, brighter skin. The difference is intensity. Glycolic is the small, fast, potent one; lactic is the larger, gentler, hydrating one. Which suits you is almost entirely a question of how much exfoliation your skin can comfortably take.
Glycolic acid: the potent one
Glycolic acid has the smallest molecule of any AHA, which lets it penetrate the surface more deeply and work more aggressively. That makes it the strongest choice for rough texture, dullness, sun damage and the look of fine lines— when it suits your skin, the smoothing and glow are noticeable. The flip side is irritation: glycolic is more likely to sting, and it’s easy to overdo, especially at higher percentages. It rewards resilient, non-sensitive skin. Our glycolic acid guide covers strengths and how often to use it.
Lactic acid: the gentle, hydrating one
Lactic acid has a larger molecule, so it works more slowly and stays more superficial — gentler on the skin and much less likely to over-exfoliate. It has one bonus glycolic doesn’t: lactic acid is mildly hydrating, which offsets the dryness exfoliation can cause. That combination makes it the go-to AHA for dry, sensitive or acid-curious beginner skin that wants smoother, brighter results without the sting.
Head to head
| Lactic acid | Glycolic acid | |
|---|---|---|
| Molecule size | Larger — stays superficial | Smallest — penetrates deeper |
| Strength | Gentler | More potent |
| Bonus | Mildly hydrating | Strongest smoothing and glow |
| Best for | Dry, sensitive, beginner skin | Resilient skin, stubborn texture and dullness |
| Sun sensitivity | Increases it — wear SPF | Increases it — wear SPF |
How to choose — and use either safely
The shortcut: sensitive or dry skin, or new to acids → lactic; resilient skin chasing more visible smoothing → glycolic. If you’re unsure, lactic is the safer starting point — you can always step up later. Whichever you choose, the rules are the same: introduce it a couple of nights a week, don’t layer it with another acid or with retinol on the same night, and because AHAs increase sun sensitivity — the FDA notes the effect can last about a week — wear sunscreen daily. Ready to buy? Our best chemical exfoliants roundup lines up real lactic and glycolic products by acid type.
General guidance, not medical advice. Barrier & Balm is written by a skincare enthusiast, not a dermatologist. For a diagnosis, a reaction, or a prescription active like tretinoin, see a qualified professional. Introduce any new active slowly and patch-test first.
Frequently asked questions
What's the difference between lactic acid and glycolic acid?
Both are alpha hydroxy acids (AHAs) that exfoliate the skin's surface, but glycolic acid has the smallest molecule, so it penetrates deeper and is the more potent of the two — great for texture and glow, but more likely to irritate. Lactic acid has a larger molecule, works more gently, and is mildly hydrating, which makes it the friendlier choice for dry and sensitive skin.
Which is better for sensitive skin, lactic or glycolic?
Lactic acid. Its larger molecule works more slowly and superficially, so it's less likely to sting or over-exfoliate, and it has a hydrating quality that offsets the dryness AHAs can cause. If your skin is sensitive or dry, start with lactic acid; save glycolic for when you know your skin tolerates acids well.
Is glycolic acid stronger than lactic acid?
Yes, at the same concentration glycolic acid is generally the stronger, deeper-penetrating AHA because its molecule is smaller. That makes it more effective for stubborn texture, dullness and sun damage, but also more irritating. Lactic acid trades some of that potency for gentleness and hydration.
Can I use lactic acid and glycolic acid together?
You usually don't need to, and combining two AHAs on the same night raises the risk of over-exfoliation. Pick one AHA for your skin type and use it a couple of nights a week. If you want to exfoliate more than one way, it's smarter to pair an AHA with a BHA on separate nights than to stack two AHAs.
Sources
- U.S. FDA — Alpha Hydroxy Acids — FDA on AHAs and increased sun sensitivity (accessed July 17, 2026)
- Chemical Peels for Skin Resurfacing — StatPearls (NCBI Bookshelf) — Reference overview of AHA/BHA exfoliation mechanisms (accessed July 17, 2026)
- American Academy of Dermatology — Skin care basics — AAD consumer guidance on cleansing, moisturizing and sun protection (accessed July 17, 2026)
Keep reading
Best chemical exfoliants
Lactic, glycolic, mandelic and a BHA compared by acid type — the real products.
See the picksAHA vs BHA
The bigger fork — surface-smoothing AHAs versus the pore-clearing BHA.
Compare the acidsGlycolic acid, explained
The most potent AHA in depth — what it does, what strength to use, and how often.
Read the guideSkincare routine for dry skin
Why lactic acid's gentle, hydrating exfoliation suits dry skin — where it fits in a routine.
See the routine