What do PHAs do for skin?

What are PHAs in skincare?

Polyhydroxy acids are one of several acid groups used in chemical peels, alongside alpha hydroxy acids and beta hydroxy acids. Chemical exfoliation removes excess surface cells using chemicals rather than the friction of a scrub, brush or sponge. Use the general chemical exfoliation approach below to introduce a PHA product.12

What results should you expect?

The useful goals for chemical exfoliation are improved surface appearance and texture. Removing excess skin cells can make skin look less dull and reduce uneven pigmentation at the surface. Do not keep increasing the acid strength to chase a result: higher concentrations can irritate and inflame skin.3

How often can you use PHAs?

For general exfoliation, keep use to no more than two or three times a week, rather than making it a daily step. Skin needs time to repair between sessions. The right frequency depends on your skin and how aggressive the exfoliation is; stronger exfoliation needs less frequent use. Follow the product's directions, and reduce use if your skin becomes red or irritated.234

How to introduce a PHA product

1. 1Review your existing routine. Prescription retinoids, retinol and benzoyl peroxide can make skin more sensitive or cause peeling, and adding exfoliation can worsen dryness or breakouts.
2. 2Test the new product on a small area first using the method below.
3. 3Start with a gentler chemical exfoliant at a lower concentration. Move to stronger concentrations only if needed, rather than treating strength as the goal.
4. 4Apply according to the product's directions, including whether to rinse it off. Never exfoliate sunburned skin or areas with open cuts or wounds.
5. 5Follow exfoliation with moisturizer to help keep skin hydrated. Use sun protection, because exfoliation can increase susceptibility to sunburn.

How to test the product first

For an at home product test, apply your normal amount to a spot about the size of a quarter on the underside of your arm or the bend of your elbow. Repeat twice daily for seven to ten days. This is a small area test, not a schedule for exfoliating your whole face. Leave the product on for its normal contact time; for a product you wash off, follow its instructions. If the area becomes red, itchy or swollen, wash the product off and do not use it again. A test can help predict a reaction, including irritation from ingredients other than the exfoliating acid.5

Are PHAs good for sensitive skin?

For sensitive skin, choose a mild chemical exfoliant rather than assuming you need a scrub. Mechanical exfoliation can be too irritating for dry, sensitive or acne prone skin. Sensitive skin is also more likely to become irritated or inflamed by any exfoliant, so testing the finished product matters. If you have a darker skin tone or develop dark marks after inflammation, avoid aggressive chemical or mechanical exfoliation because it can increase pigmentation.23

When should you stop or get help?

Stop using a product that causes a skin reaction. Gently wash it off; a cool compress or petroleum jelly can help relieve the affected area. See a dermatologist if the reaction is severe and does not improve with those measures. Repeated reactions or uncertainty about the trigger can require medical patch testing to identify the ingredient responsible.5

Do you need a PHA in your routine?

Consider it for a cosmetic concern such as surface dullness or rough texture, not simply because another step is available. If you are unsure whether exfoliation would benefit your skin, a dermatologist can help you choose an appropriate method.23