Ingredient caution: salicylic acid/BHA might cause stinging, dryness, peeling, redness and increased sun sensitivity; sulfur/zinc-based oil-control ingredients might feel drying or tight on already dry skin; preservatives such as phenoxyethanol/benzyl alcohol might sting very sensitive or compromised 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. Use a moisturiser and reduce frequency if the skin feels tight or flaky. Do not apply on broken, freshly waxed or irritated skin. Apply on slightly damp skin and follow with moisturiser if dryness occurs. Stop use if irritation persists.