If glycolic acid is the one everyone's heard of, lactic acid is the one more people should be using. It does much the same job with considerably less drama, and it has a trick the other acids don't.
What it is
Lactic acid is an alpha hydroxy acid, originally derived from milk though now usually produced by fermentation. Its molecule is larger than glycolic acid's, so it doesn't penetrate as deeply or as fast — which sounds like a disadvantage until you've experienced skin that's been over-exfoliated.
The useful quirk
Lactic acid is also a humectant, meaning it attracts and holds water in the skin. No other common exfoliating acid does this. The practical effect is that lactic acid tends to leave skin feeling softer and more comfortable rather than tight, which is why it suits drier skin so well and why it's the acid least likely to leave you regretting it.
What it's used for
Lactic acid is chosen for the appearance of dullness, rough or flaky-looking texture, and uneven tone. Skin generally looks smoother and brighter, and feels softer — a slightly different result from glycolic, which is sharper and faster but drier with it.
Strength and how to use it
Cosmetic formulas typically run from 5% to 10%, with some weekly treatments higher. Because it's gentler, many people tolerate lactic acid two or three times a week from the start, though beginning twice weekly is still sensible.
Use it in the evening on clean dry skin, and follow with moisturiser. It pairs comfortably with hyaluronic acid, ceramides and niacinamide.
As with all AHAs, alternate with retinol rather than layering, and wear daily SPF — exfoliated skin is more sun-sensitive for several days.
Who it suits
Lactic acid is the right choice if your skin is dry, sensitive or new to acids — and it's a perfectly good permanent choice, not just a stepping stone to something stronger. Plenty of people with robust skin use lactic acid indefinitely because they prefer how comfortable it leaves them.
If your skin runs oily and your concern is congestion rather than dullness, salicylic acid is the more appropriate tool.
Explore our lactic acid skincare, or see all active skincare.