My mother has chilblains. What is it in a nutshell?

Dermatology. Chilblains also known as chilblain, pernio and perniosis are small, itchy swellings on the skin, which are not painful at first, but can become painful - they are acral ulcers; ulcers affecting the extremities. They are a localized form of vasculitis that occur when a predisposed individual is exposed to cold.
Chilblains. Chilblains is cold injury to the skin. It can be related to systemic problems so a good physical exam should be done to look for possible underlying causes.