Your skin naturally sheds old cells, but that process slows with age and sun exposure. Alpha hydroxy acids loosen the substances holding surface cells together, allowing them to shed more easily. Mechanical exfoliation instead uses friction from a scrub, brush, pad or sponge. Chemical exfoliation removes dead cells without a scrubbing tool, so the bathroom can retire one piece of equipment.34
What are AHAs, BHAs and PHAs?
| Type | What it does | When to consider it |
|---|---|---|
| Alpha hydroxy acids, or AHAs | Water soluble acids that loosen dead cells at the surface. Common examples include glycolic and lactic acid. | Rough texture, uneven colour and fine lines. |
| Beta hydroxy acids, or BHAs | The skincare category commonly used for salicylic acid. Salicylic acid dissolves in oil and helps remove dead cells and excess oil inside pores. | Oily skin, blackheads and whiteheads. |
| Polyhydroxy acids, or PHAs | A related group of acids with effects similar to AHAs and less irritation. | An alternative when irritation is a concern. |
Salicylic acid is sold and discussed as a BHA, although its chemical structure does not fit the strict definition. For choosing skincare, its oil solubility is the useful distinction. Also, an ingredient having "acid" in its name does not automatically make it an exfoliator: hyaluronic acid is a sugar molecule that helps hold water in the skin.25
How do you choose a chemical exfoliator for your face?
- For blackheads, whiteheads or oily pores, consider salicylic acid. Its ability to work in oil makes it a more targeted choice for pore blockages.
- For rough surface texture and sensitivity, consider lactic acid. It is one of the gentler AHAs and acts as both an exfoliant and a moisturizer.
- For uneven colour or fine lines, consider glycolic acid. It is a strong exfoliant, so introduce it slowly.
- For dry, sensitive or acne prone skin, favour a mild chemical exfoliator over aggressive scrubbing.
- If your skin develops dark spots after irritation, or you have a darker skin tone, avoid strong exfoliation. Aggressive exfoliation can increase pigmentation.
What strength should you use?
An acid percentage is not the whole strength story. The acidity of the formula, measured as pH, and the base carrying the acid also matter. Cosmetic AHA safety recommendations use concentrations below 10% and a pH of at least 3.5 to reduce irritation. Those limits are not a personal starting dose or a reason to choose the highest percentage available.5
Routine skincare and chemical peels are different uses of these ingredients. Lower concentrations appear in creams and lotions, while concentrations above 20% are used as peels. Glycolic facial peels can range from 20% to 70%, with strength selected according to sensitivity. Do not borrow a peel's concentration, contact time or treatment schedule for an everyday exfoliating product.35
How do you use a chemical exfoliator?
- 1Check your existing routine first. Prescription retinoids, retinol and benzoyl peroxide can already cause sensitivity or peeling; adding exfoliation can worsen dryness or breakouts.
- 2Identify whether the product stays on or washes off. Both formats exist, so follow the product's directions rather than treating every acid alike.
- 3Apply gently. For a rinse off exfoliator, gentle application followed by lukewarm water is preferable to forceful rubbing or hot water.
- 4Follow exfoliation with moisturizer to counter dryness.
- 5Use SPF 30 or higher sunscreen every day. With AHAs, also wear protective clothing and limit sun exposure during use and for a week after stopping.
For glycolic acid, start once or twice a week at night and increase frequency only if your skin tolerates it. Leave on AHA preparations are generally used at night. There is no single schedule for every exfoliator: skin type and the intensity of exfoliation determine frequency, and stronger exfoliation generally needs to happen less often.123
AHA preparations can be alternated with retinoid creams or vitamin C rather than treating every application as an opportunity to combine them. If a prescription routine already leaves your skin dry or peeling, ask the clinician managing it before adding an exfoliator.13
What results can you expect, and when?
AHAs can improve roughness, uneven colour and the appearance of fine lines. Smoother texture and more even colour are realistic aims for AHA skincare, not a request for a replacement face. With sustained use, glycolic acid can also support collagen, the protein that gives skin structure. Salicylic acid is more directly useful for clearing pore blockages.235
Expect gradual changes rather than an overnight transformation. Regular use matters, and a course of AHA peels gently changes texture over a few months. That is a peel timeline, not a fixed deadline for a home serum. Ingredient benefits also do not make every finished acne product equally effective; many products sold without a prescription have limited clinical testing.37
When should you stop or get advice?
Exfoliation is optional and does not suit everyone. Skip it on sunburned skin or areas with open cuts or wounds. Stop if exfoliation leaves your skin red, irritated or increasingly dry. Burning, rash, swelling, blisters and chemical burns are reported reactions to AHA products; seek medical advice for these rather than continuing through them. A dermatologist can help decide whether exfoliation is useful if sensitivity or your skin type makes the choice unclear.146
Glycolic acid is considered safe in pregnancy. That does not make every acid, peel or combination formula interchangeable; check the specific product and any accompanying prescription treatment with your clinician.3
Where this answer comes from
- 1How to safely exfoliate at homeaad.org
- 2Facial Acids: Everything You Need To Knowhealth.clevelandclinic.org
- 3Alpha hydroxy acid facial treatmentsdermnetnz.org
- 4How to safely exfoliate at homeaad.org
- 5Applications of hydroxy acids: classification, mechanisms, and photoactivitypmc.ncbi.nlm.nih.gov
- 6Guidance for Industry: Labeling for Cosmetics Containing Alpha Hydroxy Acidsfda.gov
- 7Over-the-counter Acne Treatments: A Reviewpmc.ncbi.nlm.nih.gov
