Raynaud's Phenomenon, not to be confused with Raynaud's disease, is characterized by episodic loss of blood to the digits (fingers and toes). This is manifested by the sequential development of blanching (whitening), cyanosis (blue coloration), and rubor (redness) of the fingers and toes following exposure to the cold that is followed by rewarming.

Raynaud's Phenomenon may also be precipitated by emotional stress.

When the patient is exposed to cold air, one or more digits will appear white. This blanching represents the ischemic phase when circulation to the digits is lost. It is caused by vasospasms of the arteries in the fingers and/or toes. This phase is accompanied by sensations of cold, numbness, or paresthesias (tingling) of the fingers and/or toes. During this phase, as the arteries spasm, the capillaries and venules dilate causing blueness (cyanosis) due to the deoxygenated blood present in these vessels.

With rewarming, the vasospasm of the digital arteries is resolved and blood floes in the dilated arterioles and capillaries. This is known as reactive hyperemia and causes the digits to now appear bright red, accompanied by a sensation of warmth, and often a throbbing painful sensation during this hyperemic phase.,