(See also Structure and Function of the Skin.)

Aging results in thinning of the dermis and epidermis. The underlying fat can be lost as well. The decrease in volume and overall effectiveness of all three skin layers results in a number of important medical and cosmetic effects. The skin loses some of its elasticity. It becomes drier due to impaired barrier function and decreased production of essential oils such as sebum. The number of nerve endings in the skin decreases, so sensation is diminished. The number of sweat glands and blood vessels decreases as well, reducing the skin's ability to respond to heat exposure. The number of melanocytes tends to decrease with aging, so the skin has less protection against ultraviolet radiation. All of these changes make the skin more susceptible to damage and slower to heal.

Sun damage produces most of the skin changes that people commonly associate with aging (see Overview of Sunlight and Skin Damage). Long-term exposure to the ultraviolet radiation in sunlight is responsible for fine and coarse wrinkles, irregular pigmentation, brown and red spots, and the rough texture of sun-exposed skin.