Millennial Skin

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Exfoliating acids have a reputation problem — too many people try one, their skin freaks out, and they swear off the whole category forever. But if that sounds familiar, there’s a very good chance you never tried the right acid for your skin type. PHAs (polyhydroxy acids) are the third generation of exfoliating acids, and they’re engineered to be gentler, more hydrating, and far less likely to irritate — without skipping the actual exfoliation. Here’s everything you need to know to decide if PHAs belong in your routine.

What are PHAs (polyhydroxy acids)?

PHAs are a family of exfoliating acids that came after AHAs and BHAs — think of them as the next evolution in chemical exfoliation. The most common ones you’ll see on labels are gluconolactone, lactobionic acid, and galactose. These molecules occur naturally in the body and in food, and they’ve been studied in clinical dermatology for decades. That long track record is part of what makes them trustworthy — the science behind them isn’t new, even if they’re just now going mainstream in everyday skincare.

How do PHAs work on skin?

Like all exfoliating acids, PHAs work by loosening the bonds that hold dead skin cells together, allowing them to shed and reveal fresher skin underneath. The critical difference from AHAs like glycolic acid comes down to molecular size: PHA molecules are significantly larger, so they penetrate slowly and stay near the skin’s surface rather than driving deep into the dermis. That’s what makes them so much gentler — you get the turnover without the aggressive tingling, irritation, or post-exfoliant sensitivity that stronger acids can trigger. PHAs are also humectants, meaning they attract water to the skin while they work, leaving it feeling hydrated rather than stripped.

PHA vs. AHA vs. BHA: what’s actually different?

All three are acids that exfoliate, but they behave differently and suit different skin concerns. AHAs (glycolic, lactic, mandelic) are water-soluble and penetrate deeply — effective for texture, tone, and hyperpigmentation, but harder on sensitive skin. BHAs (primarily salicylic acid) are oil-soluble and go into the pore lining, making them the go-to for congestion, blackheads, and acne-prone skin — you can read more about how that works in our deep dive on salicylic acid. PHAs stay closest to the surface, exfoliate gently, and double as humectants — making them the most beginner-friendly and sensitive-skin-friendly option of the three.

What do PHAs actually do for your skin?

The exfoliation is the headline benefit, but PHAs bring more than that. Because they’re humectants, they draw moisture into the upper layers of your skin while they work — so instead of feeling tight after use, your skin feels smoother and more comfortable. PHAs also carry antioxidant properties, helping neutralize environmental damage from UV exposure and pollution over time. And unlike stronger acids that can compromise your skin barrier with overuse, PHAs actually help support barrier function. If you’ve been curious about why a healthy barrier matters so much, the post on what skipping toner does to your skin barrier is a good primer on why you want to protect it — and why choosing gentler actives is part of that.

Who should use PHAs?

The short answer: anyone whose skin doesn’t tolerate stronger acids well. PHAs are the exfoliating acid most dermatologists point toward for people with rosacea, eczema-prone skin, or generally reactive complexions that flare up with most actives. They’re also the smart starting point if you’re new to chemical exfoliation and want to introduce your skin to the category without overwhelming it. That said, you don’t need to have “problem” skin to benefit — even people with normal or combination skin who just want a sustainable, everyday-friendly exfoliant will find PHAs easy to work into a routine without babying it afterward.

How to use PHAs in your skincare routine

Start with 2 to 3 nights per week, applied after cleansing and any toning steps, before moisturizer. Give your skin 3 to 4 weeks of consistent use before you evaluate results or think about increasing frequency — consistency matters more than intensity here. Some people eventually work up to nightly use without issues, but there’s no need to rush it. Because PHAs increase photosensitivity like all exfoliants, always apply SPF 30 or higher the next morning. If you’re also using a retinoid, alternate nights rather than layering both on the same evening; keep actives simple until you know how your skin responds, then adjust from there.

The best PHA products to try in 2026

The range of solid PHA products has expanded a lot over the last two years. Here are four worth trying across different formats and price points — all from brands known for getting the formulations right.

PHA FAQ

Are PHAs safe for rosacea-prone skin?

PHAs are one of the only exfoliating acids that dermatologists generally feel comfortable recommending for rosacea-prone skin. Their large molecule size means they don’t penetrate deep enough to trigger the inflammatory response that smaller acids can cause. As always, patch test before full application and introduce slowly — every complexion is different — but PHAs are the most well-tolerated exfoliant in this category.

Can I use PHAs every day?

Many people can, especially with lower-concentration products. Start at 2 to 3 nights per week and increase gradually if your skin stays calm — no excess flaking, tightness, or redness. If you eventually want to try daytime use, make sure you’re following with broad-spectrum SPF every single morning without exception.

Do PHAs help with dark spots and hyperpigmentation?

Yes, though more gradually than AHAs. By accelerating surface cell turnover, PHAs help fade post-inflammatory hyperpigmentation and general dullness over time. For faster results, pairing PHAs in your evening routine with a vitamin C serum in the morning is a reasonable combination that won’t overwhelm sensitive skin.

Can PHAs be layered with retinol?

You can use both in the same overall routine, but keep them on separate nights rather than stacking them in the same session. Alternating — PHAs on some evenings, retinol on others — lets each ingredient do its job without pushing your skin barrier past what it can handle. Once your skin is well-adjusted to both individually, some people do layer them, but separate nights is the safer starting point.

How long before I see results from PHAs?

Most people notice smoother texture within 2 to 4 weeks of consistent use. Brighter tone and reduced dullness typically follow in the 4 to 8 week range. Because PHAs work gradually by design, patience is part of the deal — but the upside is that the results come without the adjustment period of redness and peeling that stronger acids often require.