Raynaud's disease occurs when the small arteries (arterioles) that serve the fingers, toes, ears, or nose go into spasm. When arterioles go into spasm, they cut off blood supply and cause digits (fingers and toes) or the tips of the ears or nose to turn white or blue and lose feeling.
Sometimes this can happen as part of a pattern seen with other diseases, in which case it is called Raynaud's phenomenon or secondary Raynaud's. When this happens alone, without signs of any other underlying disease, it is called Raynaud's disease or primary Raynaud's.
People with Raynaud's phenomenon tend to get it either in both hands or in both feet. Raynaud's disease tends to appear in all of the hands and feet. About 3 out of 4 sufferers of primary Raynaud's disease are women aged between 15 and 40.