What Is It?
Raynaud's phenomenon is a blood vessel disorder. The condition is also called Raynaud's disease or Raynaud's syndrome.
When healthy people are in a cold environment, the tiny blood vessels in their skin constrict, or narrow. This is an effort by the body to conserve heat.
In people with Raynaud's phenomenon, that natural response to cold is exaggerated. The tiny blood vessels go into spasm, narrowing and reducing the blood flow to the affected areas. This response, called vasospasm, is seen most often in the fingers and toes. But it also can occur in the ears, cheeks and nose.