What causes dry skin?

In healthy skin the sebaceous glands release an oily substance called sebum, which keeps the skin moist, supple and waterproof. Sebum, together with other natural oils, known as lipids, and natural moisturising factors (NMFs), form a barrier known as the hydro-lipid system. This barrier acts to keep 'foreign substances' out of our bodies and keeps water inside the body for as long as possible. In dry skin this barrier is no longer intact so the skin suffers from increased moisture loss. Dry skin becomes particularly prevalent as we get older, as our bodies don't produce these natural oils so effectively. Babies and young children are also often susceptible to dry skin because the oil producing glands haven't developed properly.

Whilst some people have an inherited predisposition to dry skin, there are also a number of external factors which can contribute. These are more harmful in skin which is already dry and where the hydro-lipid barrier system is impaired. Dry, cold and windy weather can cause the skin to peel, flake and thicken, as can the sun. Central heating, air conditioning, poor ventilation, chemicals, detergents, soap and solvents can all play a part in causing dry skin. Excessive contact with water also reduces the skin's natural moisturizing factors.

As people get older, the number of sebaceous glands that give out a type of oil in the skin are reduced, as is the skin's ability to hold moisture. It appears both the skin's ability to hold water and how well it protects the body, depend on the amount of fat the outer layer of skin contains. This outer layer is known as the epidermis. Genes also play a role. If relatives suffer from dry skin, you are more likely to develop the condition. In extreme cases, fish-like scaling of the skin is sometimes seen (ichthyosis). Over-use of soap and water, a dry, warm indoor climate, excessive sunbathing and other environmental effects have a great influence on how dry the skin can become.

More information on dry skin (xerosis)