Glycolic Acid

Glycolic acid is 果酸（甘醇酸）(guǒ suān / gān chún suān) in Chinese — 果酸 is the umbrella term for AHAs and 甘醇酸 the specific acid; Taiwan uses 甘醇酸, and the chemical name is 乙醇酸. It's the smallest AHA, exfoliating dead cells to brighten and smooth skin.

No. It only speeds shedding of already-aged dead cells and doesn't harm living cells or the dermis; regular long-term use actually builds a more resilient barrier. Overuse or too-high concentrations can temporarily weaken barrier defenses, though, so beginners should go low and slow.

Beginners: once weekly at night; after 3–4 weeks with no obvious stinging, consider twice. Long-term users can do 2–3x weekly. Sensitive skin should stay at weekly or longer intervals. Keep contact under 15 minutes, then always rinse it off.

Sunscreen and moisture, above all. Skin is more fragile for 24–48 hours after use: skip heavy makeup and other irritating actives that day and layer a hydrating serum plus cream. Diligent sunscreen the next day is non-negotiable — otherwise rebound darkening and post-inflammatory pigmentation are likely.

Home products run 4–10% at higher pH with short contact time — mild by design. Professional peels run 20–70% at lower pH for 5–15 minutes: dramatic results, but they need trained hands and recovery time. Both work; choose based on your skin's condition and tolerance.

Start at 4–5% with a pH of 3.5–4 or above — beginner-friendly territory. After 2–4 weeks of good tolerance, step up to 6–8%. Don't jump straight to 10%: over-irritation damages the barrier and sets you back.