This is a condition in which the smallest arteries that bring blood to the fingers or toes constrict (go into spasm) when exposed to cold or from an emotional upset. Smoking cigarettes or working with vibrating machinery also can cause these episodes. The small veins are usually open, so the blood drains out of the capillaries (KAP'ih-lair"eez). The result is that the fingers or toes become pale, cold and numb. If there's a spasm in the small veins and blood is trapped in the capillaries, the fingers or toes turn blue as the blood loses its oxygen.

People who have experienced what appears to be Raynaud's syndrome are encouraged to see their physician to confirm the diagnosis and, if necessary, to get proper treatment. Most people only need to make minor lifestyle changes. In some cases, however, vasodilators (medications that relax and widen blood vessels) may be prescribed to keep the blood vessels from constricting.

Raynaud's (ra-NOZ') syndrome is also sometimes called Raynaud's phenomenon or Raynaud's disease.