Ingredient caution: salicylic acid/BHA might cause stinging, dryness, peeling, redness and increased sun sensitivity; niacinamide is usually gentle but might cause tingling or flushing in very reactive skin; sulfur/zinc-based oil-control ingredients might feel drying or tight on already dry 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. Start slowly if your skin is sensitive and avoid combining too many new actives at once. Use a moisturiser and reduce frequency if the skin feels tight or flaky. Use lukewarm water, do not scrub, and follow with moisturiser. Stop use if irritation persists.