Dermatology is the medical specialty concerned with the health of the skin, hair, nails, and mucous membranes. A dermatologist is a doctor who specializes in diagnosing and treating diseases like acne, psoriasis, and skin cancer, as well as cosmetic conditions and aging skin. They use various medical and surgical procedures to manage these conditions for patients of all ages. Cosmetics are products applied to the body to cleanse, beautify, promote attractiveness, or alter appearance, including makeup (lipstick, mascara), skincare (lotions, creams), hair care (shampoo, dye), and personal hygiene items (deodorant, soap). They work by temporarily changing the look or feel of skin, hair, nails, or teeth, and range from simple powders and oils to complex chemical formulations, all intended for external use for aesthetic or hygienic purposes.