There are several possibilities. The most likely explanation is
Raynaud’s phenomenon. This is a condition in which blood flow to
the fingers is temporarily impaired. Sometimes other parts of
the body are affected, such as the toes, ears or nose. Raynaud’s
is thought to develop because of an exaggerated constriction of
the arteries that supply blood to the fingers. We all have
nerves that send signals to the small arteries of the fingers
instructing the arteries to open or constrict. For example, the
arteries normally narrow when you’re cold. This is the body’s
way to conserve heat. For unknown reasons, the tendency for
arteries to constrict in the cold is exaggerated in people with
Raynaud’s. After being exposed to the cold, artery constriction
initially leads to whiteness of the fingers, then blueness and
then, as the artery opens up again, redness. Usually this
sequence occurs over a number of minutes and the finger soon
appears normal again. Besides cold, emotional stress and certain
medications can also t