What causes wrinkles ?

Constant movement of muscles causes the skin to crease and because skin becomes less elastic over time, repeated facial expression will create visible lines and wrinkles. Frown lines appear between the eyebrows and crow's feet, lines that radiate from the corners of the eyes, develop because of permanent small muscle contractions in and around the eye area.

Habitual facial expressions form other characteristic lines such as the deep lines from the sides of the nose to the sides of the mouth (known as naso labial folds) and small vertical lines around the lips. There are other contributing factors, as a person ages, skin undergoes significant changes: 

• The cells divide more slowly and the inner layer of skin - the dermis - starts to thin
• Fat cells beneath the dermis begin to atrophy (diminish)
• The underlying network of elastin and collagen fibres, which provides support for the surface layers, loosen and begin to disintegrate.
• Skin loses its elasticity, taking longer to spring back to its initial position after movement.
• The sweat and oil secreting glands become smaller, depriving the skin of their protective water-lipid emulsions. The skin's ability to retain moisture then diminishes and it becomes drier, flaky and less flexible.
• Gravity exacerbates the situation, contributing to the formation of jowls around the jawline and drooping eyelids.
• The ability of the skin to repair itself diminishes with age.

 There are also environmental and lifestyle factors that contribute to the formation of wrinkles:

Exposure to ultraviolet radiation contributes to the breakdown of collagen and elastin as well as dehydration of the skin. Overall, exposure to ultraviolet - referred to as UVA or UVB  radiation - emanating from sunlight, accounts for about 90% of the symptoms of premature skin ageing, and most of these effects occur by the age of 20.

 Cigarette smoke produces free radicals and is known to accelerate wrinkles and ageing skin disorders.

 Air pollution in particular ozone, which is a common air pollutant, may be a particular problem for the skin. One study has reported that it might deplete the amount of vitamin E in the skin and this vitamin is an important anti oxidant. 

Rapid weight loss can also cause wrinkles by reducing the volume of fat cells that cushion the face. This not only makes a person look gaunt, but can cause the skin to sag.