Aging

• An inevitable factor leading to the wrinkling of skin is aging. As the outer layer of the skin --- or epidermis --- ages, the cells become thinner and are unable to bind together as effectively. This lessened cohesiveness of the cells leads to a loss of moisture in the skin. To make matters worse, the number of epidermal cells decreases by 10 percent every 10 years, and they repair themselves more slowly. Less collagen is produced, sweat glands decrease and the skin loses much of its elasticity. All of these factors lead to wrinkling and sagging of the skin.
  
  

Sunlight

• According to the U.S. Environmental Protection Agency, Ultraviolet A and Ultraviolet B waves in sunlight cause as much as 90 percent of the symptoms related to premature wrinkling. The degree of damage caused by the sun depends on the amount of radiation exposure throughout a lifetime and also on the pigmentation of a person's skin. Sunlight damages the epidermis by thinning it and making it easier for damage to occur to the second layer of skin, or dermis. This dermal damage leads to a collagen breakdown at a significantly higher rate than that caused by aging alone. Also, the skin's attempt to repair itself can lead to "sun scarring," which can develop into wrinkles over time.
  
  

Free Radicals

• Free radicals are particles of unstable oxygen in the air that lack an electron. These particles "steal" electrons from cells in the skin when they come into contact. The skin cell then must wait until it comes into contact with a particle containing an electron so that it can regain its lost electron. This process repeats continuously and causes wrinkles by triggering the production of a skin enzyme called metalloproteinasis, which breaks down collagen. The degenerative free radical process is accelerated by exposure to sunlight, cigarette smoke and air pollution.
  
  

Muscle Use

• Over time, repeated facial expressions cause much-used skin to loosen and begin to sag. Frowning, smiling, creasing the forehead and other expressions cause crows feet and creases about the face to increase in prevalence as the tiny muscles near the eyes and throughout the face are permanently contracted. The effects of gravity make these lines more apparent due to increased sagging and drooping of the skin.