Glycolic acid is the benchmark exfoliant – the one every other acid gets compared to. It's also the one most likely to be overdone. Here's how to get the results without the fallout.
What it is
Glycolic acid is an alpha hydroxy acid derived from sugar cane. Its distinguishing feature is molecule size: glycolic has the smallest molecule of any AHA, so it penetrates faster and further than its relatives. That's the source of both its effectiveness and its reputation for stinging.
What it's used for
Glycolic is chosen for the appearance of dullness, uneven texture, the look of fine lines and general roughness. Skin typically looks brighter and feels noticeably smoother, and it's one of the few actives where you can often see a difference after a single use — which is precisely why people are tempted to use it more often than they should.
Strength and format
Cosmetic products generally range from around 5% to 10% for regular use, with weekly treatments going higher. Professional peels operate at concentrations well above anything sold over the counter, and belong in a clinic.
Format matters as much as percentage. Cleansers rinse off within a minute, making them the gentlest option. Toners and liquid exfoliants stay on and do considerably more. Serums are the most concentrated leave-on route. Weekly masks and pads are a good middle path for people who'd rather do one deliberate treatment than a nightly routine.
How to use it
Once or twice a week to begin with, in the evening, on clean dry skin. Build slowly — three times a week is a comfortable destination for most people, and nightly glycolic is more than most skin needs.
Follow with a proper moisturiser. Hyaluronic acid, ceramides and squalane all pair well and keep skin comfortable.
Two things to keep apart from it: retinol (alternate nights instead) and other exfoliants. Using glycolic and salicylic on the same evening isn't twice as effective, just twice as likely to leave your barrier struggling.
Daily SPF is essential. Glycolic makes skin more sensitive to sunlight for several days after use.
Glycolic or lactic?
Choose glycolic if your skin is robust, you've used acids before, and you want the fastest visible change in smoothness and brightness. Choose lactic acid if your skin is drier, more reactive, or new to exfoliation — it's gentler and hydrates as it works. There's no shame in the gentler option; consistency beats intensity every time with exfoliation.
Explore our glycolic acid skincare, or see all active skincare.