Some causes of a swollen right foot may be an injury, such as a sprained ankle or foot, lymphedema, or infection, according to WebMD. Blood clot and medication side effects are other possible causes of a swollen foot. Swelling of only one foot is usually due to an injury or infection, while illnesses that affect the entire body such as kidney or heart disease can lead to fluid buildup and swelling in both feet, explains MedicineNet.
A sprain is one of the most common injuries that causes swelling in both the ankle and foot and occurs when ligaments stretch too far or snap, states WebMD. Ligaments are the bands of tissue that keep the bones in alignment. Sprains range in severity from grade one which occurs when the ligaments stretch but do not tear to grade three which occurs when the ligament completely tears. The chances of getting a sprain is greater for those who play sports, especially sports that require changing direction or are on uneven surfaces and those who wear shoes that do not fit. Additional symptoms of a sprain are pain and bruising.
Some infections that may cause swelling in the foot are an abscess or cellulitis, reports MedicineNet. Antidepressants and calcium channel blockers are two categories of medications that may result in swollen feet as a side effect.