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Raynaud’s phenomenon is a condition that causes the blood vessels in the extremities to narrow, restricting blood flow. The episodes or “attacks” usually affect the fingers and toes. In rare cases, attacks occur in other areas such as the ears, tongue, or nose. An attack usually happens from exposure to cold temperatures or emotional stress. There are two types of Raynaud’s phenomenon—primary and secondary. The diagnosis between the two types is most commonly made with a device called nailfold capillaroscopy, where the doctor looks at your skin at the bottom of your fingernails under a microscope. The primary form has no known cause, but the secondary form is related to another health issue, especially autoimmune diseases like lupus or scleroderma . The secondary form tends to be more serious and to need more aggressive treatment. In most people, lifestyle changes such as staying warm keep symptoms under control, but in severe cases, repeated attacks lead to skin sores or gangrene (death and decay of tissue). The treatment depends on how serious the condition is and whether it is the primary or secondary form.