Dry skin. Coloured scanning electron micrograph (SEM) of dry skin from the knuckles. Two hairs are seen at lower left. While all skin is shed continuously, dry skin is shed at a higher rate, leading to a flaky appearance. Dry skin may be caused by a poor diet or exposure to irritants. It is also very common in the winter when low humidity leaves skin dry and itchy. Magnification: x40 when printed at 10 centimetres wide.