Raynaud’s phenomenon (RP) is an exaggerated constriction of blood vessels to the extremities, triggered by cold temperatures or emotional stress. As a result of this spasm, the hands (and often the feet and sometimes the ears and nose) change color. They will often first become white and then blue. Often, along with the color change will be discomfort or even severe pain.
Color changes of the extremities can have other causes, especially if these changes are present only on one side of the body (RP usually involves both sides). Especially when the problem is not symmetrical, it’s important to make sure another cause, such as a clot in an artery or hardening of the arteries, is not present. Also, RP is different from simply having cold hands. RP includes both coolness and the characteristic white and blue color changes. Some people have only one color change in the cold, such as only white or only blue, and those people are considered to have “possible” Raynaud's phenomenon.