Ingredient caution: glycolic acid/AHA might cause stinging, dryness, peeling, redness and increased sun sensitivity; vitamin C/ascorbic derivatives might cause tingling, redness or irritation in sensitive skin; niacinamide is usually gentle but might cause tingling or flushing in very reactive skin; cleansing surfactants might cause dryness, stinging or tightness if overused. 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. Start slowly if your skin is sensitive and avoid combining too many new actives at once. Use lukewarm water, do not scrub, and follow with moisturiser. Stop use if irritation persists.