Ingredient Guide
AHA (Alpha Hydroxy Acids)
AHAs are a family of water-soluble acids, including glycolic and lactic acid, used to exfoliate the skin’s surface and improve dullness, uneven texture and some types of visible pigmentation.
Evidence profile
How confident is this recommendation?
Confidence is shown in plain categories, not a numerical trust score.
Well-studied as a category, though specific evidence strength varies by which AHA and what concentration.
Professional peels use much higher concentrations under supervision.
This is where most consistent evidence exists.
AHAs work at the skin’s surface; deeper concerns generally need other approaches.
Glycolic, lactic, mandelic and other AHAs are not always tested head-to-head under the same conditions.
What it is
A category of exfoliating acids, not a single ingredient.
AHA stands for alpha hydroxy acid, a category that includes glycolic acid, lactic acid, mandelic acid and others. They work by loosening the bonds between dead skin cells on the surface, helping reveal smoother-looking skin underneath.
Different AHAs vary in molecule size, which affects how deeply and how quickly they penetrate; glycolic acid, being the smallest, tends to be the most potent and potentially irritating.
Evidence at a glance
Useful evidence, with important limits.
Surface texture and dullness
Multiple studies support AHA exfoliation for improving the look of rough or dull skin.
Limit: Results depend heavily on concentration, pH and consistency of use.
Mild uneven pigmentation
Regular use may gradually improve some types of superficial discoloration.
Limit: AHAs alone are usually less effective for pigmentation than combination approaches with sunscreen and other actives.
Concentration guide
Match the concentration to your experience level.
| Concentration or form | How to interpret it | Practical use |
|---|---|---|
| 5% | A gentle starting point for AHA-naive skin. | Two to three nights weekly to start. |
| 8–10% | A common, moderately active leave-on strength. | For those with established tolerance. |
| Professional peel strengths (20%+) | Applied and monitored by a trained professional. | Not appropriate for home use without supervision. |
Skin Candid view: Start low and build tolerance gradually. A lower concentration used consistently often outperforms a high concentration used inconsistently due to irritation.
How to use it
Introduce gradually and always pair with sunscreen.
Go slowly: Over-exfoliating can worsen the very texture and tone issues AHAs are meant to improve.
Using it with other ingredients
Reduce routine complexity before testing combinations.
BHA (salicylic acid)
Avoid combining strong AHA and BHA products on the same night while building tolerance.
Sunscreen
The essential daily pairing given increased sun sensitivity.
Side effects and caution
Irritation and sun sensitivity are the main considerations.
- Stinging, redness and mild peeling are common when starting out or using too frequently.
- Increased sun sensitivity is well established; daily SPF is essential.
- Avoid combining with other strong exfoliants or retinoids on the same night initially.
- Discontinue if irritation becomes persistent or severe.
Frequently asked questions
AHA (Alpha Hydroxy Acids), without the pressure to tolerate everything.
What’s the difference between AHA and BHA?
AHAs are water-soluble and work mainly at the skin surface; BHA (salicylic acid) is oil-soluble and can penetrate into pores, making it often preferred for oily or acne-prone skin.
Which AHA is best for beginners?
Lactic acid is often considered gentler than glycolic acid due to its larger molecule size and some hydrating properties.
Can I use AHA every day?
Most people do better starting two to three times weekly and building up gradually based on tolerance.
Related decisions
Continue from the question you are actually trying to solve.
Sources reviewed
Primary evidence and medical guidance behind this page
- American Academy of Dermatology: How to safely exfoliate at home
- American Academy of Dermatology: How to select a sunscreen
- PMC: Sunscreens and photoageing, a review of current literature
Sources support the general editorial conclusions shown here. They do not prove that every product containing this ingredient will produce the same result.