The average adult has 21 square feet of skin (2 sq m) which weighs 7lb (3.2 kg) and has approximately 300 million skin cells. Skin is thickest on the palms & soles (1.2mm to 4.7mm) and thinnest on the lips and around the eyes.

Facial skin is approximately 0.12mm thick and on the body is about 0.6mm.

The skin reflects your general health and social behaviour. Situations which affect your health can have an important effect on your skin, for example cigarette smoking causes ageing and wrinkling of the skin with time.

As in other mammals, human skin is composed of an outer layer, the epidermis, and an underlying layer of fibrous tissue called the dermis.

Beneath the dermis is the subcutaneous fat. The epidermis is constantly growing from the bottom upwards and the dead skin cells (stratum corneum) are shed (usually invisibly) from the surface. This whole process normally takes about 52-75 days but can be much quicker in some skin diseases such as psoriasis.

If your skin changes suddenly and with no apparent reason it may be a sign of ill health, e.g. the sudden onset of dry skin with coarse hair and weight gain may mean your thyroid gland is underactive.

Looking after your skin

Keeping the skin clean is important to prevent infections and odours but excess washing can particularly in people with a tendency to dry skin already, cause loss of oil in the outer layers of the skin and provoke dermatitis. Similarly, chemicals such as petrol, white spirit and detergents can cause dry and damaged skin leading to hand dermatitis. The young and the elderly have more sensitive skin because their barrier is less well formed. People who have had eczema, asthma or hay fever as children are more prone to these problems in adult life.

Protection form the sun

The major cause of ageing of our skin is ultraviolet light. Ultraviolet causes pigmentation changes e.g. liver spots or sunspots, broken blood vessels, thinning of the dermis and wrinkling of the skin. In order to prevent this, protection of the skin against ultraviolet light is required. Certain skin types are more susceptible to these effects. Most at risk are those with fair skin that burns easily.

We are aware of no studies that show any benefits of sunbed tanning, there are a number of short and long term health risks associated with their use.

Many sunbed users believe that skin damage is avoided provided their skin does not burn. Unfortunately this is not true since damage can be shown to occur with UVA exposures below those necessary for burning.