Ingredient caution: 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; UV filters might sting around the eyes or irritate very sensitive skin; rich oils, butters or occlusive emollients might feel heavy or clog pores in acne-prone/oily skin. Do a patch test before applying. 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. Patch test near the jawline first, avoid the eye corners, and remove gently at night. Use a small amount first and avoid applying on active acne if it feels greasy. Stop use if irritation persists.