As uncomfortable as it can be, primary Raynaud’s is not dangerous and is not as severe as secondary Raynaud’s, which has a later onset, usually starting after age 35 or 40. In rare severe cases in which blood flow is chronically diminished, secondary Raynaud’s can result in skin ulcers and even gangrene that require surgery.

A doctor can distinguish between the two by putting a drop of oil on the skin at the base of the fingernail and examining the area under a microscope. The presence of enlarged or malformed capillaries in this area, the nail fold, indicate an underlying connective tissue disease. Two blood tests, the antinuclear antibody test and the erythrocyte sedimentation rate, can aid in diagnosing an underlying cause of Raynaud’s, which can then be treated.

Raynaud’s affects parts of the body that have a characteristic circulatory pattern: a high density of direct connections between arterioles — small vessels that branch out from arteries — and venules, or small veins. These connections, called arterio-venous anastomoses, govern circulation in the nonhairy surfaces of the body, bypassing capillaries that normally bring blood to the skin, Dr. Flavahan explained last year in Nature Reviews: Rheumatology.

When people with Raynaud’s are exposed to cold or are under stress, normal nervous system-induced constriction of the arterioles in these anastomoses is enhanced and may temporarily cut off blood flow to the affected parts, causing them to turn white and feel cold and numb. When the areas are rewarmed and the spasm resolves, blood flow resumes, often causing tingling or throbbing.

There is no cure for Raynaud’s, and remedies supported by solid scientific evidence are few. But there are well-established measures that can minimize its effects. Most important of these is to stay warm. For me that means wearing multiple insulating layers, especially on my arms and legs, so that any extra heat generated can transfer to my hands and feet. It’s a trick I learned ice-skating and skiing and that I’ve applied to cycling and hiking in New York winters. Wearing a hat and neck gaiter and a wind-resistant outer garment is also very helpful.

Mittens keep hands warmer than gloves. I store my hand coverings on the radiator and my boots under it when not in use. My short arms have found a purpose, enabling me to further protect my hands by pulling sleeves down over them. This winter I will try heated gloves fueled by rechargeable batteries that last a lot longer than chemical hand-warmers. I also keep gloves next to the freezer to use when removing frozen foods. Some people even wear gloves when they sleep, and from fall through mid-spring, I wear socks to bed.

If you smoke, don’t. Nicotine causes a drop in skin temperature that adds to the problem. Certain medications that constrict blood vessels can also make matters worse. They include beta-blockers; many cold remedies, especially those that contain pseudoephedrine; some migraine remedies; and some blood pressure medications.