Ingredient caution: lactic acid/AHA might cause stinging, dryness, peeling, redness and increased sun sensitivity; niacinamide is usually gentle but might cause tingling or flushing in very reactive skin; rich oils, butters or occlusive emollients might feel heavy or clog pores in acne-prone/oily skin; preservatives such as phenoxyethanol/benzyl alcohol might sting very sensitive or compromised 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. Start slowly if your skin is sensitive and avoid combining too many new actives at once. Use a small amount first and avoid applying on active acne if it feels greasy. Do not apply on broken, freshly waxed or irritated skin. Stop use if irritation persists.