Thrombophlebitis is swelling of a vein caused by a blood clot. It usually occurs in your legs. If the affected vein is just beneath the skin, the condition is usually not dangerous. A clot in a deeper vein, called deep vein thrombosis, can break loose and cause a serious problem in the lung, called a pulmonary embolism, or a heart attack or stroke.

Sitting still for a long time can make you more likely to get thrombophlebitis. Some medicines and disorders that increase your risk for blood clots can also lead to thrombophlebitis. Common symptoms are

• Warmth and tenderness over the vein
• Pain or swelling in the part of the body affected
• Skin redness

Treatment includes medicines to ease pain and inflammation, break up clots and keep new clots from forming. Keeping the affected area raised and applying moist heat can also help. If you are taking a long car or plane trip, take a break, walk or stretch your legs and drink plenty of liquids.

"Thrombo" means "clot." Phlebitis is inflammation of a vein. Thrombophlebitis (throm-bo-fluh-BI-tis) occurs when a blood clot causes inflammation in one or more of your veins, typically in your legs. On rare occasions, thrombophlebitis (often shortened to "phlebitis") can affect veins in your arms or neck.

The affected vein may be near the surface of your skin, causing superficial thrombophlebitis, or deep within a muscle, causing deep vein thrombosis (DVT). A clot in a deep vein increases your risk of serious health problems, including a dislodged clot (embolism) traveling to your lungs and blocking a pulmonary artery (pulmonary embolism).

Thrombophlebitis often is caused by prolonged inactivity, such as from sitting during a long period of travel in an airplane or automobile or from lengthy bed rest after surgery. Such inactivity decreases blood flow through your veins and may cause a clot to form. Paralysis, certain types of cancer and use of the hormone estrogen also may lead to thrombophlebitis. An inherited tendency for blood clots places you at higher risk of thrombophlebitis.

You can use self-care methods to ease pain and reduce your risk of clots. Various treatments, including medications and surgery, also are available for thrombophlebitis.