Heredity and age are the main reasons why we get wrinkles, while smoking, UV rays and air pollution are the important factors that contribute to the premature development of wrinkles. So what is called premature aging. In premature aging, free radicals exert harmful oxidation on healthy cells and other structures in the skin. These oxidative processes are called oxidative stress. Oxidative stress plays a crucial role in skin aging. The skin's antioxidant properties are important defense mechanisms to reduce the consequences of oxidative stress. External causes of oxidative stress are often more powerful than the skin's antioxidant defenses can handle. This causes premature aging. This means that you get signs of aging and impaired function in the skin faster than what the body's own processes would indicate.