Alpha Hydroxy Acids: Your Guide to Glycolic, Lactic, and Mandelic Acid

The Three Main AHAs Compared

Glycolic Acid (from sugarcane)

• Molecular size: Smallest AHA — deepest penetration
• Potency: The most effective AHA with the most research behind it
• Best for: Sun damage, fine lines, wrinkles, hyperpigmentation, rough texture. Anti-aging powerhouse.
• Concentrations: 5-10% for home use, 20-70% for professional peels
• Drawback: Most irritating AHA. Not ideal for sensitive or very dark skin (higher PIH risk).
• At higher concentrations: Stimulates dermal collagen production — one of the few topicals (besides retinoids) proven to do this

Lactic Acid (from milk or fermentation)

• Molecular size: Medium — moderate penetration
• Potency: Gentler than glycolic with comparable surface-level results
• Best for: Dry skin, sensitive skin, beginners, hydration + exfoliation combo
• Unique benefit: Acts as a humectant — attracts water to the skin while exfoliating. Also stimulates ceramide production, supporting the skin barrier.
• Concentrations: 5-10% for home use, 20-50% for professional peels
• Drawback: Less potent than glycolic for deep wrinkles and significant photodamage

Mandelic Acid (from almonds)

• Molecular size: Largest — shallowest penetration, slowest absorption
• Potency: Gentlest AHA, most tolerable
• Best for: Very sensitive skin, rosacea-prone skin, darker skin tones (lowest PIH risk), acne
• Unique benefit: Also has antibacterial properties — effective for acne (similar to benzoyl peroxide in some studies). Its slow absorption means more even, controlled exfoliation.
• Concentrations: 5-10% for home use, 20-50% for professional peels
• Drawback: Least potent for anti-aging concerns

Choosing Your AHA

How to Use AHAs Safely

• Start low: 5% concentration, 2-3 times per week at night
• Increase gradually: After 4 weeks, increase frequency to nightly or move to a higher concentration
• Apply to dry skin: Water can increase penetration and irritation
• Sunscreen every morning: AHAs increase photosensitivity by up to 50%. SPF 30+ is mandatory.
• Don't combine with retinoids on the same night initially — alternate nights until your skin adjusts
• Signs of over-exfoliation: Stinging, persistent redness, peeling, increased sensitivity — reduce frequency if these occur

Frequently Asked Questions

Can I use AHAs every day?

At low concentrations (5% glycolic, 5% lactic), many people tolerate daily use. Higher concentrations (10%+) are better at 2-3 times weekly. Your skin's tolerance is the guide — if it's not irritated, daily is fine.

How long before I see results?

Improved brightness and smoothness: 1-2 weeks. Fading dark spots: 6-8 weeks. Fine line improvement: 8-12 weeks. Significant collagen changes (with glycolic): 3-6 months.

Can I use AHA and BHA together?

Yes, but not on the same application initially. Alternate nights (AHA one night, BHA the next) or use BHA in the morning and AHA at night. Some experienced users layer both without issues — listen to your skin.