A must-have product, sunscreen helps protect the skin from the sun’s UV rays, which may cause skin cancer and signs of aging. Apply every day after cleansing and exfoliating, and before makeup. Apply to cleaned skin at least 15 minutes before going outside (30 minutes before going in water), and reapply every two hours if you remain outside. Physical sunscreens (consisting of zinc or iron oxide or titanium dioxide) physically block UV rays from damaging the skin while chemical sunscreens (usually ending in -ate or -one) absorb the ultraviolet light, then break it down. Be aware that physical sunscreens are less likely to irritate the skin, but can be thicker and pastier.