Ingredient caution: PHA, glycolic acid/AHA, salicylic acid/BHA might cause stinging, dryness, peeling, redness and increased sun sensitivity; vitamin C/ascorbic derivatives might cause tingling, redness or irritation in sensitive skin; humectants such as hyaluronic acid/glycerin are usually gentle but might feel sticky or tight if not sealed with moisturiser. Do a patch test before applying. First-time users should start 3–4 times a week, avoid using it with retinol or other exfoliating acids in the same routine, and apply sunscreen daily. First-time users should start 3–4 times a week and avoid layering with strong exfoliating acids if the skin stings. Apply on slightly damp skin and follow with moisturiser if dryness occurs. Avoid during pregnancy or breastfeeding unless your doctor approves. Stop use if irritation persists.