You’re late for work on a cold December day, so you hop in your car without giving it a chance to warm up. You let out a squeal as you touch the steering wheel — it’s freezing, but you forgot your gloves. You’ll just have to deal with cold hands and hope the heat kicks in soon.

Cold, tingly, or numb fingers or toes are actually a typical and helpful body response: Your body is trying to maintain its core temperature by limiting the heat leaving through the skin. It does this by narrowing blood vessels and decreasing blood flow to the surface of your body — such as your feet, hands and nose — to keep heat near the core.

But in some people with the condition known as Raynaud’s phenomenon, the body takes this too far in areas like the fingers, toes, tips of the nose and ears, and even the knees and nipples. This can be painful — and in some cases, this process can be permanently damaging.

Below are answers to five important questions about Raynaud’s.

I’ve watched my fingers rotate through a few colors. Do I have Raynaud’s?

Along with feelings of cold, numbness or pain, the toes and tips of the fingers can turn white, then blue in Raynaud’s. After warming up, the skin can turn red as blood rushes back in, a process that typically takes 15 to 20 minutes. Depending on your skin color, these color changes may be harder or easier to see.

Though cold and stress are the main triggers for these changes, they’re even more likely when some sort of pressure is applied — like gripping that cold steering wheel or grabbing a pizza out of the freezer in the grocery store. This also tends to happen when people quickly go from a warm to a cold environment, like stepping into an air-conditioned building on a sweltering summer day.

What are the different kinds of Raynaud’s?

The cause of primary Raynaud’s is not fully understood. But it may be caused by changes in how the small blood vessels in your extremities — or the nerves connected to these blood vessels — respond. Other than the uncomfortable or painful symptoms, this condition won’t harm you.

Secondary Raynaud’s is part of or related to another condition or treatment. You could have it because of a traumatic injury like frostbite, certain medications like those used to treat attention-deficit/hyperactivity disorder, or an autoimmune condition such as scleroderma.

Scleroderma is a condition that involves the hardening and tightening of the skin. It also may damage other organs such as the lungs, kidneys and heart.

How do I know if I have primary or secondary Raynaud’s?

Because Raynaud’s may be a sign of an autoimmune disorder such as scleroderma, or other conditions, you’ll want to know which type you’re dealing with. Some differences:

Are there tests that can help tell the difference between primary and secondary Raynaud’s?

Yes. Along with the above differences, your healthcare team can use tests to help figure out whether you likely have primary or secondary Raynaud’s.

One clue comes from blood tests. These tests can look for certain antibodies often found in people with autoimmune disorders, including scleroderma.

Another test zooms in on the problem, looking at your blood vessels to see if they’ve changed. This procedure, known as nailfold capillaroscopy, examines the very small blood vessels called capillaries near your fingernails. A drop of oil or lubricant is placed on your cuticle, then a powerful microscope or magnifier is used to search for deformities, swelling or missing capillaries. These changes indicate that you may have or may develop an autoimmune disease, such as scleroderma.

Neither nailfold capillaroscopy nor antibody testing can say with certainty that you have primary or secondary Raynaud’s. But when used together in combination with a review of your symptoms and a physical exam, they can help determine if an underlying autoimmune condition, such as scleroderma, is present that may need further evaluation and monitoring.

What can I do to prevent Raynaud’s flares?

If you have Raynaud’s, there are lifestyle changes that can ease your symptoms.

• Bundle up! It’s not only cold fingers or feet that trigger Raynaud’s — you’re at risk if your core temperature goes down. Keep your core warm in colder conditions — in addition to your hands and feet — by wearing loose-fitting, layered clothing, as well as warm socks, hats, scarves, and gloves or mittens. Using hand and boot warmers may also be helpful.
• Watch the meds. Stay away from tobacco and stimulant medications such as decongestants and amphetamines, as these can exacerbate Raynaud’s.

These strategies may not be enough for some people with Raynaud’s — especially in colder climates and months — so you may need to take certain medications such as calcium channel blockers. Those with secondary Raynaud’s also might need treatment for the underlying condition.

Hopefully, understanding why your fingers and toes react the way they do with cold and pressure can go a long way toward being prepared and reducing your discomfort.