Reference · Exfoliants
Acid concentration guide
The right glycolic, lactic, mandelic, and salicylic percentages for daily use — and where "home product" ends and "in-office peel" begins.
Acid concentration reference chart
"Daily use" means a typical leave-on serum or toner. "Stronger" means space it out and watch for irritation. "Peel" strengths are performed by professionals and are listed only for context, not for home use.
| Acid | Type | Daily use | Stronger | In-office peel | Best for |
|---|---|---|---|---|---|
| Glycolic acid (AHA) | AHA — smallest molecule | 5–10% | 10–15% (space out) | 20–70% (in-office) | Sun damage, dullness, fine lines; deepest-penetrating AHA |
| Lactic acid (AHA) | AHA — larger, hydrating | 5–10% | 10–12% | 20–50% (in-office) | Dry or sensitive skin; gentler, also humectant |
| Mandelic acid (AHA) | AHA — largest molecule | 5–10% | 10–12% | 20–40% (in-office) | Sensitive, acne-prone, and deeper skin tones; slow, low-irritation |
| Salicylic acid (BHA) | BHA — oil-soluble | 0.5–2% | 2% (max OTC leave-on) | 20–30% (in-office) | Oily, congested, blackhead- and acne-prone skin; gets into pores |
| Azelaic acid | Dicarboxylic acid | 10% (OTC) | 15–20% (Rx) | n/a | Rosacea, redness, post-acne marks; well tolerated, pregnancy-friendlier |
| PHA (gluconolactone / lactobionic) | Polyhydroxy acid | 4–10% | 10% | n/a | The most sensitive skin and barrier repair; largest molecules, mildest |
✦More acid is not more results. Past your skin's tolerance, higher percentages just trade exfoliation for a damaged barrier.
What to use by experience level
| Experience | Pick | Frequency | Note |
|---|---|---|---|
| First-timer / sensitive | PHA, mandelic 5%, or lactic 5% | 1–2 nights/week | Lowest irritation; build tolerance before stepping up |
| Beginner | Glycolic 5–7% or salicylic 2% (if oily) | 2–3 nights/week | The most common starting point for most skin |
| Intermediate | Glycolic 8–10% or lactic 10% | 2–3 nights/week | Alternate with retinoid nights; do not stack same night |
| Advanced | Glycolic 10–15% (occasional) | 1–2 nights/week | Watch for over-exfoliation; less is more |
Acids increase sun sensitivity — always wear broad-spectrum SPF 30+ the next morning. Do not layer a high-strength acid on the same night as a retinoid unless your skin is well-adapted. This chart is educational, not medical advice; a board-certified dermatologist can tailor strengths to your skin and any conditions.
Frequently asked
What percentage of glycolic acid should a beginner use? +
Beginners do best with glycolic acid at about 5–7% used 2–3 nights a week. Daily-use leave-on products generally sit in the 5–10% range; anything above roughly 10% should be spaced out, and concentrations of 20% and higher are professional in-office peels, not daily home products.
What is the strongest salicylic acid I can buy over the counter? +
For leave-on over-the-counter products, salicylic acid (a BHA) tops out around 2%. Wash-off cleansers may go a little higher, and spot treatments can reach 5–10% on individual blemishes, but 2% is the standard effective daily leave-on strength. Stronger salicylic peels are done in-office.
Which acid is gentlest? +
Polyhydroxy acids (PHAs) like gluconolactone are generally the gentlest because their large molecules penetrate slowly. Among AHAs, mandelic and lactic acid are gentler than glycolic because their molecules are larger and absorb more slowly. Salicylic acid is oil-soluble and best for congestion rather than general gentleness.
Can I use AHA and BHA together? +
You can, and some products combine them, but using high-strength AHA and BHA together raises the risk of over-exfoliation, stinging, and a damaged barrier. If you are newer, alternate them on different nights rather than layering both at full strength.
How often should I exfoliate with acids? +
For most people, 2–3 times per week is plenty; very sensitive skin may want once a week. Daily acid use is only for tolerant skin and lower concentrations. Signs you are overdoing it include tightness, stinging, shininess, and increased sensitivity — back off if you see them.
Are these acids safe in pregnancy? +
Azelaic acid and low-strength glycolic or lactic acid are often considered acceptable, while salicylic acid is usually limited to low-percentage, leave-off use. Recommendations vary, so confirm any acid with your OB-GYN or a board-certified dermatologist before using it while pregnant or breastfeeding.
Related: What is glycolic acid? · What is salicylic acid? · Glycolic vs lactic acid · Mandelic acid guide · Ingredient layering chart · All reference charts