Blood vessels are supposed to constrict when they're exposed to cold temperatures; that's the body's way of preserving heat. But in people who have Raynaud's, the blood vessels undergo vasospasms that reduce circulation to the extremities, causing fingers, toes, and even the tips of your nose or ears to turn white. When they recover, the extremities turn red and tingle.

Being outdoors in frigid weather, however, isn't the only thing that can set off an attack. Stress, cigarette smoking, and even a stroll through the freezer section of a supermarket can trigger an attack. Raynaud's may be a primary condition that exists on its own, or it can be a secondary condition in people who have fibromyalgia, lupus, or scleroderma.

If you do experience Raynaud's, try to warm up the affected body parts quickly. Persistent severe Raynaud's can cause a reduction in blood flow severe enough to injure or kill the involved tissues.