Exfoliation is the process of removing dead skin cells to promote cell turnover and improve skin texture. Done right, it helps with tone, absorption, and clog prevention; overdone, it destroys the skin barrier.
Exfoliation splits broadly into physical (scrubs, cleansing brushes) and chemical (acid-based ingredients) methods. Current dermatology views the chemical method as more even and less irritating.
Comparing chemical exfoliating ingredients
### AHA (Alpha Hydroxy Acid)
A water-soluble ingredient that breaks the bonds between surface keratinocytes to promote shedding.
Main ingredients
- Glycolic acid: smallest molecule, strong penetration, most researched
- Lactic acid: less irritating than glycolic, also moisturizing
- Mandelic acid: least irritating, suits sensitive skin
Effects: surface exfoliation, pigmentation improvement, smoother texture, fine lines
Caution: increased UV sensitivity → sunscreen essential
Suitable skin: dry, pigmented, photoaging-concerned skin
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### BHA (Beta Hydroxy Acid)
A lipid-soluble ingredient. Its affinity for sebum lets it penetrate into pores and dissolve sebum and keratin together.
Main ingredient: salicylic acid 0.5–2%
Effects: pore keratin removal, sebum control, acne prevention, blackhead improvement
Anti-inflammatory effect: salicylic acid also has anti-inflammatory action, helping reduce acne redness
Suitable skin: oily, acne-prone, large-pore skin
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### PHA (Poly Hydroxy Acid)
Larger molecules than AHA with slower penetration. It acts only on the surface and is the least irritating.
Main ingredients
- Gluconolactone
- Lactobionic acid
Effects: very gentle exfoliation + antioxidant + moisturizing
Suitable skin: sensitive, atopic, dry skin, exfoliation beginners
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Recommended ingredients & frequency by skin type
| Skin type | Recommended ingredient | Recommended frequency |
|-----------|------------------------|------------------------|
| Oily/acne-prone | BHA (salicylic acid 1–2%) | 3–4x/week |
| Dry/pigmented | AHA (glycolic, lactic) | 1–2x/week |
| Sensitive | PHA or low-strength lactic | 1x/week or biweekly |
| Combination | T-zone BHA, dry areas AHA or PHA | 2–3x/week |
How to use it properly
pH: AHA is effective at pH 3–4, BHA at pH 3–4. High pH greatly reduces effect.
Time: Mostly use at night. Using during the day without sunscreen risks UV sensitivity.
Layering: Avoid using on the same night as retinol. Alternate instead.
Introduction: Start at the lowest concentration/frequency. Evaluate after 4–6 weeks.
Symptoms of over-exfoliated skin
- Severe tightness within 10 minutes of cleansing
- Stinging when applying products
- Skin looks glossy but reddens easily
- The paradox of even more visible flaking
- Worsening acne
If these appear, stop exfoliating products immediately and focus on barrier recovery. With exfoliation, "more = better" isn't true — keeping the right interval is key.