#Chemical Exfoliation

Chemical exfoliation is the category where over-use causes more damage than any other in skincare. I have triaged dozens of barrier-compromised routines that started with someone reading that glycolic acid is good for skin and concluding that daily 10 percent glycolic toner is the move. It is not. The acids that earn shelf space are powerful, evidence-based, and need careful introduction. The good news is that the rules are simple, the ingredients are well-studied, and a routine that respects them produces visible change inside a few months.

The acid family, mapped

AHA, BHA, PHA: the acid family tree is the foundational piece. AHAs (alpha hydroxy acids) are water-soluble and act on the skin surface to dissolve corneocyte bonds. Glycolic is the smallest molecule and the most penetrating; lactic is gentler with hydrating side effects; mandelic is the largest, slowest, and most tolerable for sensitive skin. BHAs (beta hydroxy acids, mainly salicylic) are oil-soluble and penetrate inside pores, making them ideal for acne, congestion, and blackheads. PHAs (polyhydroxy acids: gluconolactone, lactobionic acid) are the largest molecules of all, slower-acting, and gentlest, often tolerated by skin that flares on AHAs. Picking the right family is the first decision, and almost every other choice flows from it.

Choosing between AHAs

Glycolic vs lactic acid: which AHA belongs in your routine is the most useful decision piece. Glycolic at 5 to 10 percent has the strongest evidence for cumulative effects on pigmentation, fine lines, and texture, but it is also the most irritating. Lactic at 5 to 10 percent gives a softer ramp and adds humectant action because the molecule itself draws water into the corneocyte layer. Mandelic acid: the gentle AHA for sensitive and acne-prone skin is the underrated entry: gentle enough for reactive skin, with antibacterial properties that help acne-prone faces, and slow enough that overuse is harder. For most people new to AHAs, I recommend starting with lactic or mandelic and graduating to glycolic only if needed. The reverse path (starting with glycolic and discovering tolerance) is how most barrier damage begins.

The BHA case for acne and oily skin

Salicylic acid: how it works, how to use it, who should skip it covers the BHA that earns its place in nearly every adult-acne routine. Salicylic at 0.5 to 2 percent is one of the best-evidenced acne ingredients available without a prescription, and its oil solubility means it penetrates into the pore where the acne is actually forming, not just the surface. The American Academy of Dermatology includes it in their over-the-counter recommendations for acne. Cautions: avoid during pregnancy at higher concentrations, and skip if you have an aspirin allergy, since salicylic acid is structurally related to acetylsalicylic acid and can trigger a similar reaction. PHAs come in as the safety-conscious option for everyone else.

The contrarian take on frequency

Here is the take that runs against beauty media: most users need a chemical exfoliant two to three times a week, not daily. The pursuit of "glass skin" through daily acid use is the single most common cause of barrier damage I see in reader emails. Skin's natural turnover cycle is roughly 28 to 45 days depending on age, and accelerating that with daily aggressive acid use does not give 10x the results, it gives a compromised barrier and chronic sensitivity that then takes months to repair. Two or three nights a week of a well-chosen acid, alternating with retinoid nights and rest nights, outperforms daily use by a wide margin over the 12-week arc. Polyglutamic acid vs hyaluronic acid: the 4x claim, tested closes the hub with the hydrating acid often paired alongside exfoliating ones, and the honest read of the marketing claim that polyglutamic acid holds four times more water than hyaluronic does. Pairing a hydrating acid with an exfoliating acid is one of the simplest ways to reduce irritation while keeping the turnover benefits, and it is one of the few stacking moves I recommend without much hesitation. The rest of the routine should stay quiet, and your skin will reward the restraint over the next three months. The acids that get oversold in skincare are usually the acids used at the wrong frequency, in the wrong combination, on a barrier that was already asking for less work to begin with.