Episodic vasospasm (constriction of small arteries) of the digits. It is characterized by 3 phases:
Digital Blanching (white)	Cyanosis (blue)	and Ruborization (red)
after cold exposure and rewarming and can also be induced by anxiety or stress. This condition is primarily confined to the fingers and toes. Blanching represents the ischemic (lack of adequate blood flow) phase of the phenomenon, caused by digital artery vasospasm. Cyanosis results from deoxygenated blood in capillaries and venules (small veins). Upon rewarming and resolution of the digital vasospasm, a hyperemic phase ensues, causing the digits to appear red. Raynaud's can be a primary or secondary disorder.

Primary Raynaud's phenomenon is also called Raynaud's disease. Criteria for Raynaud's disease include episodic digital ischemia, absence of arterial occlusion, bilateral distribution, absence of symptoms or signs of other diseases that also cause Raynaud's phenomenon, and duration of symptoms for 2 years or longer. Most people with Raynaud's disease develop symptoms before they reach 40 years of age. It can occur in young children. Raynaud's disease affects women three to five times more frequently than men. Prevalence is lower in warm climates than in cold climates