Ingredient caution: niacinamide is usually gentle but might cause tingling or flushing in very reactive 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. Start slowly if your skin is sensitive and avoid combining too many new actives at once. Apply on slightly damp skin and follow with moisturiser if dryness occurs. Stop use if irritation persists.