What Is the Cause of One Swollen Foot?

Trauma, such as that caused by torn tendons, strains or fractures, is the most common cause of swelling in a foot, explains About.com. Arthritis often causes localized swelling in the feet, and there are a number of types of arthritis, including gout, which typically causes a swollen big toe. Osteoarthritis is another type of arthritis that causes swelling, and it generally occurs in the joint.

Vein problems usually cause swelling in the lower extremities, including the feet, according About.com. Swelling in the foot can also be a sign of a blood clot, which is a potentially serious condition known as deep vein thrombosis. Infections may also cause swelling in the foot and often appear on the skin, in the toenails or between the toes. Swelling can also indicate a severe case of athlete's foot.

Some medications may cause a swollen foot, including testosterone drugs, corticosteroids and birth control pills, states About.com. Many pregnant women also experience swelling in the feet, which is due to the release of pregnancy hormones and an increase of fluids in the bloodstream. Certain medical conditions, such as liver disease, heart disease and diabetes, can also cause swollen feet.

Foot swelling is typical during pregnancy, but abrupt swelling can indicate preeclampsia, says WebMD. In pregnancy scenarios when the swelling is concurrent with abdominal pain, headaches and nausea, medical attention needs to be sought as soon as possible. Hormone replacement therapy, blood pressure medications, antidepressants and diabetes medications all carry the potential side effect of swollen feet. If the swelling is severe enough, dosages or medications may need to be adjusted.