Chilblains are an abnormal reaction of the small blood vessels in the skin to changes in temperature. The abnormal reaction results in a painful reddish itchy patch that then turns a darkish blue colour as waste products build up.
Normally when the feet get cold, the small blood vessels in the skin close up to conserve heat and then when the skin is warmed up after that those small blood vessels open up. This is a normal process.
When a chilblain occurs those small blood vessels for some unknown reason stay closed longer than they should as the skin warms up. This means that the metabolic demands of the skin is not being met by the circulation from those small blood vessels. Then, typically, the blood vessels do rapidly open leading to a red patch on the skin associated with inflammation. With the release of inflammatory mediators that lesion on the skin becomes itchy and painful. As the metabolites in the skin build up from this process it changes to a darker colour. This will eventually heal up. It will become chronic if another chilblain occurs as the result of repeated cold exposures and not taking precautionary measures.
Chilblains are not caused by “cold”; they are caused by a too rapid warming up of the foot after it is cold and the blood vessels that were constricted are not given time to open by slowly warming the foot. Poor circulation is not the cause of chilblains, it is how the circulation responds to changes in temperature that is the problem.
The prevention of chilblains is by firstly not getting cold and then if you do get cold to let the foot warm up slowly. The treatment of chilblains is to protect the area and stimulate the circulation and prevent another one from occurring.