These sore itching, inflamed, and frequently swollen patches of skin occur most commonly on the back of fingers or tops of toes. Sometimes they crop up on the ears, outer thighs, and other parts of the body that are subject to cold and/or pressure. Normally occurs in colder weather.

The cause is restriction of the circulating blood supply in the capillaries (the tiniest blood vessels at the very end of the circulatory system), which leads to lack of oxygen and nutrients and consequent cell damage. Prevention is the only cure.