Thanks to lower gas prices, Americans are hitting the road in record numbers this summer.

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But for men and women with varicose veins, traveling long distances in cars or airplanes requires special precautions. That's because anyone with varicose veins is at a slightly higher risk for deep vein thrombosis (DVT) during trips that take 4 hours or longer.

DVT is a condition that results from the formation of a thrombus, or blood clot, in a vein deep within the body. Clots that travel to the lungs from the legs are known as pulmonary emboli (PE).

Symptoms of DVT include pain, tenderness or swelling of the calf or thigh (typically in one leg), and increased temperature and redness of that same body part.

If you're diagnosed with DVT, the main goal is to prevent the blood clot from growing or moving to your lungs as a life-threatening PE, where it can block the flow of blood.

Who is at risk for DVT

There are many risk factors for DVT and PE, says Thomas Wakefield, M.D., head of vascular surgery and a director at the University of Michigan Frankel Cardiovascular Center.

Among them:

•  Age. Older individuals are more likely to have DVT, particularly those with poor mobility or a serious illness such as cancer. 

• Recent trauma, surgery or hospitalization that causes immobility or paralysis. These can cause blood flow in the veins to be slow, making the blood more likely to clot.

• Family history or personal history of DVT or PE.

• Pregnancy and the period around delivery.

• Oral contraceptives and hormone replacement therapies. Estrogen in these sources can cause the blood to clot more easily.

• Obesity, infections and chronic medical conditions.

• Inherited and acquired blood clotting abnormalities.

• Smoking (according to some studies).

Tips for reducing risk of blood clots while traveling  

Wakefield offers the following tips for individuals that plan to be seated for long periods of time:

• Wear compression stockings.

• Get up and move about whenever possible.

• Periodically pump your legs up and down while seated.

• Drink lots of fluids and wear loose-fitting clothes that do not restrict blood flow.

• Try not to cross your legs for extended periods of time.

• Avoid drinking alcoholic beverages while in transit.

• Taking an aspirin before traveling may be helpful.

"Any and all methods of reducing your risk of DVT are important," says Wakefield. "If you plan to travel and have concerns about your risk of getting a blood clot, be sure to talk with your doctor or a health care professional."