Ingredient caution: PHA 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; alpha arbutin might cause tingling, dryness or redness in sensitive skin. 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. First-time users should start 3–4 times a week and pair with sunscreen, because pigmentation care works best with UV protection. Stop use if irritation persists.