A wrinkle is a fold, ridge or crease in the skin. Skin wrinkles typically appear as a result of aging processes such as glycation or, temporarily, as the result of prolonged (more than a few minutes) immersion in water. Wrinkling in the skin is caused by habitual facial expressions, aging, sun damage, smoking, poor hydration, and various other factors. With prolonged water exposure, the outer layer of skin starts to absorb water. The skin doesn’t expand evenly, causing it to wrinkle. Depletion of water in the body, as occurs with dehydration, can also cause this puckering of the skin. Cortisol causes degradation of skin collagen.