The swelling of your feet or ankles is called edema in medical term. There are a number of causes like a twisted ankle, allergic reactions, blood clotting or congestive heart failure. Congestive heart failure is where the heart weakens and pumps less blood. This causes fluid to slowly build up and creating leg edema.
Edema itself is not harmful but is uncomfortable. When your foot, leg or face is swelling it is best to tend to it right away. There are a lot of natural remedies for swollen feet and ankles. You can try taking magnesium supplement, exercise to improve circulation, soak it in tonic water or salt water, warm compress, elevate your feet, and many more.