Acid-based cosmetic formulas support the turnover of dead cells at the surface and are often studied for their potential effects on texture, evenness of tone and radiance. There are three main families:
AHA: Alpha-Hydroxy Acid
AHA stands for alpha-hydroxy acid. Examples you may encounter on a label:
- Glycolic acid: Listed as Glycolic Acid in the INCI list.
- Lactic acid: Listed as Lactic Acid in the INCI list.
- Mandelic acid: Listed as Mandelic Acid in the INCI list.
The FDA notes that AHA exfoliation depends on the acid, concentration, pH and other ingredients. Molecular size alone cannot identify the strongest or gentlest finished product.
BHA: Beta-Hydroxy Acid
The main member of the BHA family is Salicylic Acid (salicylic acid). Unlike AHAs, it is oil-soluble, which allows it to reach into pores filled with sebum.
Rinse-off and leave-on products have different directions. Do not treat one percentage as a universal safety or efficacy threshold for BHA products; the FDA also advises against exceeding the instructed frequency.
PHA: Polyhydroxy Acid
PHAs (most commonly Gluconolactone and Lactobionic Acid) are larger-molecule relatives of the AHA family. They combine surface action with a mild moisture-retaining profile.
In a 12-week study by Edison and colleagues, a gluconolactone regimen was associated with less burning and stinging than the glycolic acid regimen tested. This does not guarantee the safety of every PHA product or establish suitability for rosacea or atopic dermatitis.
Choosing by Profile
- Acne-prone or oily skin: An acid family alone does not determine treatment. Account for acne products you already use.
- Dark-spot-prone skin: The AAD warns that aggressive exfoliation can increase dark spots in some people.
- Dry or dehydrated skin: Exfoliation can worsen dryness; choosing an acid is not the same as addressing moisture needs.
- Sensitive skin or an existing skin condition: Do not assume an acid is suitable; discuss whether exfoliation is appropriate with your dermatologist.
Three Practical Reminders
- Follow the directions. There is no weekly schedule for every acid. Stop using it and seek medical advice if irritation or prolonged stinging develops.
- Do not overlook sun protection. The FDA recommends sunscreen, protective clothing and limiting sun exposure during AHA use and for a week afterwards. For help reading labels, see the sunscreen guide.
- Account for your current routine. Adding exfoliation alongside retinol, prescription retinoids or benzoyl peroxide can increase dryness and irritation.
This article is for information only; it does not provide a medical diagnosis, treatment or a guarantee of safety. If you have sensitivities, are pregnant or have particular circumstances, you are advised to discuss your decisions with your own doctor.