PHA (Polyhydroxy Acid)

PHAs (polyhydroxy acids) are a class of exfoliating acids with larger molecules that work gradually on the skin's surface. They provide exfoliation while simultaneously supporting hydration, making them an excellent choice for sensitive skin or those new to exfoliants.

• Best time

  Evening is the easier place for it, though it suits either time of day.

• How often

  Follow the frequency on the pack. There is no need to build up slowly.

• Where it goes

  A leave-on step: after cleansing, before your moisturizer.

• Where to apply

  Across the whole face rather than dabbed onto single spots, and keep it away from the eye area. Rinse with plenty of water if any gets in your eyes.

• Sun

  Wear sunscreen over the areas you have applied it before spending time in the sun.

• Alongside others

  Follow it with a moisturizer. It draws water to the surface, so it sits comfortably alongside humectants and barrier creams.

• Stick to one exfoliating product at a time — two acids in the same session is what usually causes the tightness.

• Keep it to a different evening from retinol.

• What to expect

  Mild tingling or dryness can turn up.

• If it doesn't suit

  Use it on fewer days rather than pushing through, and stop if the tingling or dryness persists.

Discontinue use if unexpected discomfort occurs.

Six situations change whether PHA (Polyhydroxy Acid) suits your skin right now. Each one is either a reason to skip it, a reason to go slowly, or nothing to watch for.

Fragile or Sensitive

Go slowly

Recent Facial or Laser

Go slowly

Prone to Redness

Go slowly

Dry or Itchy Patches

Go slowly

Recent Shave or Wax

Go slowly

Maternity & Nursing

No caution

Fragile or Sensitive — Use it less often — or stop — if it feels uncomfortable, and keep it off skin that’s broken, cut or sunburned.

Recent Facial or Laser — Wait until your skin feels settled before reintroducing — typically 7 to 14 days after a facial or laser appointment.

Prone to Redness — Try it on a small area first, and use it less often — or stop — if you notice stinging or extra redness.

Dry or Itchy Patches — Keep the rest of your routine well moisturized, and use it less often — or stop — if you notice tightness or itching.

Recent Shave or Wax — Avoid for 24 hours after waxing, threading, or dermaplaning.

Region	Most a cosmetic may contain
United States	No explicit cap
Canada	18% (total mono-AHA, pH ≥3.5)
European Union	No explicit cap
Great Britain	No explicit cap
India	No explicit cap
Brazil	No explicit cap
Japan	No explicit cap
South Korea	No cap (leave-on products must be pH 3.0–9.0)
Kenya	No explicit cap
Namibia	No explicit cap
Ukraine	No explicit cap
Georgia	No explicit cap
Australia	No explicit cap
United Arab Emirates	No explicit cap
Kuwait	No explicit cap
Hong Kong	No explicit cap
Singapore	No explicit cap
Brunei	No explicit cap
Jordan	No explicit cap
Trinidad & Tobago	No explicit cap

Where a figure appears, that is the maximum strength allowed or advised for pha (polyhydroxy acid) in that market — some are set in cosmetics regulation, others are the ceiling a cosmetic safety panel recommends. Where no figure appears, the market either sets no cosmetic maximum or handles this ingredient outside its cosmetic rules. These are limits, not targets — the right strength for a formula is the formulator's decision.

Open a market to see the rulebook its figure comes from. Those notes describe each market's own rules as we read them, current to August 24, 2026; the linked documents are the authority, and nothing here is legal advice.

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Serums · 5

A'PIEUEgg PHA Pore Serum - 55g$11.61Also on StylevanaSKINFOODBlack Sugar Perfect PHA Ampoule - 50ml$12.32Also on StylevanaTIRTIRPHA 15% Serum - 30ml$18.75Also on Stylevanaharuharu wonderCentella 3% PHA Gentle Liquid Exfoliating Serum - 120ml$19.60Also on YesStyleAPRILSKINCalendula 10% PHA+AHA Resurfacing Serum - 30ml$22.90

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What is PHA (Polyhydroxy Acid)?

A gentle exfoliating acid that lifts away dull surface build-up while holding water at the surface, so skin looks smoother without looking stripped.

What else is PHA (Polyhydroxy Acid) called?

On a label you may see PHA, Polyhydroxy acid, Gluconolactone and Lactobionic acid.

Is PHA (Polyhydroxy Acid) an AHA or a BHA?

Neither. It is a PHA — short for polyhydroxy acid.

When should you apply PHA (Polyhydroxy Acid)?

Morning or evening. Evening is the easier place for it, though it suits either time of day.

How often can you use PHA (Polyhydroxy Acid)?

Up to daily, all over the face, not the eye area.

Where do you apply PHA (Polyhydroxy Acid)?

All over the face, not the eye area. Keep it off your lips too.

Can you use PHA (Polyhydroxy Acid) around the eyes?

No. PHA (Polyhydroxy Acid) goes all over the face, not the eye area.

Does PHA (Polyhydroxy Acid) make skin more sensitive to the sun?

No. PHA (Polyhydroxy Acid) is not flagged as increasing sun sensitivity.

What should you not use with PHA (Polyhydroxy Acid)?

Space it apart from Eye-area retinol, Other exfoliants, Retinoids and Vitamin C.

Who should avoid PHA (Polyhydroxy Acid)?

Go slowly with Fragile or Sensitive, Recent Facial or Laser, Prone to Redness, Dry or Itchy Patches and Recent Shave or Wax.

Is there a cosmetic limit for PHA (Polyhydroxy Acid)?

Only some regions set one. The maximum strength for PHA (Polyhydroxy Acid) in a cosmetic is 18% (total mono-AHA, pH ≥3.5) in Canada. No maximum is set in the United States, the European Union and Great Britain. A cap is a limit on the rules, not a signal to use more.

Everything on this page traces to the sources listed below — regulators' own publications and published studies. Where the evidence does not answer a question, it is left unanswered.

Our review is AI-assisted and is not a named expert's opinion. Last reviewed August 7, 2026.

Think something here is out of date or wrong? Email us at wiki@skinintelligence.ai with your reasoning and where you read it. We read what people send, and we update the page when the sources support it.