In This Guide
AHA vs BHA vs PHA: Key Differences
| Type | Best Skin Type | Works On | Strength | Sun Sensitivity |
|---|---|---|---|---|
| AHA (glycolic, lactic) | Dry, dull, mature | Surface texture, dark spots | Medium–Strong | High — always use SPF |
| BHA (salicylic) | Oily, acne-prone | Inside pores, blackheads | Medium | Moderate |
| PHA (gluconolactone) | Sensitive, dry | Surface, gentle brightening | Mild | Low |
Alpha Hydroxy Acids (AHAs)
AHAs are water-soluble acids that dissolve the "glue" holding dead skin cells together on the surface. They're derived from natural sources: glycolic acid from sugarcane, lactic acid from milk, mandelic acid from almonds.
Glycolic Acid
Smallest molecule → deepest penetration → most powerful results. Best for: texture, fine lines, hyperpigmentation. Start at 5–8% and work up to 10–12%.
Lactic Acid
Gentler than glycolic with a larger molecule size. Also a humectant, so it hydrates while it exfoliates. Best for: dry skin, beginners, sensitive types. 5–10% is effective.
Mandelic Acid
Largest AHA molecule, slowest penetration, gentlest effect. Also antibacterial, making it surprisingly effective for acne-prone skin. Best for: combination skin, melasma, sensitive skin that can't tolerate glycolic.
Paula's Choice Skin Perfecting 8% AHA Gel Exfoliant
Glycolic acid at an effective 8% concentration in a gentle, leave-on gel formula. One of the most consistent exfoliants in the industry with decades of research behind it.
Check Price on Amazon →Beta Hydroxy Acids (BHAs)
The only BHA used in skincare is salicylic acid. Unlike AHAs, salicylic acid is oil-soluble — meaning it can penetrate through the sebum in your pores to dissolve blackheads and whiteheads from the inside out. This makes it uniquely effective for acne-prone skin.
- 0.5–1%: Gentle, daily-use concentration. Great for sensitive acne-prone skin.
- 2%: Standard OTC maximum. Most effective for blackheads and active breakouts.
- 3%+: Prescription strength, used for keratosis pilaris and more stubborn conditions.
Paula's Choice Skin Perfecting 2% BHA Liquid Exfoliant
The #1 recommended BHA by dermatologists worldwide. Salicylic acid at 2% in a lightweight leave-on formula. Visibly reduces blackheads, smooths bumpy texture, and controls shine.
Check Price on Amazon →Polyhydroxy Acids (PHAs)
PHAs are the newest and gentlest category. Their larger molecular size means slower, more superficial penetration — which means less irritation. They're perfect for beginners, sensitive skin, and anyone who finds AHAs too harsh.
Common PHAs: gluconolactone, lactobionic acid, galactose. Bonus: they're also antioxidants and humectants.
How to Build a Safe Exfoliation Routine
Week 1–2: Use 1x per week in the evening only. Apply to clean, dry skin. Moisturize after. Use SPF the next morning (AHAs especially increase photosensitivity).
Week 3–4: Increase to 2x per week if no irritation. Watch for redness, excessive flaking, or tightness — these signal over-exfoliation, not progress.
Month 2+: Settle into 3–4x per week or as your skin tolerates. Never exfoliate on the same evening as retinol or vitamin C (with strong AHAs).