Have you noticed that your skin becomes dry and itchy in the winter months? This is due to the low humidity associated with colder weather. Indoor heating also contributes to the problem, making the skin of the face and body feel very unpleasant. Everyone is familiar with the appearance of dry skin. Fine lines become more visible, the skin appears dull and flaky and is rough to the touch. Severely dry skin may have a crackled appearance, similar to old china. Most of the time, dry skin is just uncomfortable but, occasionally, it can lead to problems such as cracking and infection. Dry skin most commonly occurs on the arms and legs, but can also affect the face, hands and trunk of the body. Dermatologists refer to the condition as xerosis.

What causes dry skin?

To understand what causes the skin to become dry, it is important to understand the structure of the skin and its multiple layers. The outermost layer, or stratum corneum, is what you see when you look in the mirror. This layer acts rather like plastic wrap, sealing moisture into the inner layers. It is composed of dead skin cells and natural oils (lipids) produced by the underlying, live skin. The primary purpose of the stratum corneum is twofold: to prevent moisture evaporating from the lower skin layers, and to form a barrier preventing germs from entering the body. Trapped between the lipids and the dead skin cells are droplets of moisture that keep the stratum corneum functioning properly and looking smooth, supple and hydrated.

Dry skin happens when the level of water in the stratum corneum is too low. This may be caused by a reduced lipid content, causing water to evaporate, or by cold, dry winter air drawing moisture from the skin. Dry air produced by indoor heating also robs the skin of needed moisture. When the stratum corneum dries out, it shrinks, causing tiny cracks to form. These give rise to itching and expose the underlying skin to germs in the environment.