There are several reasons for foot swelling: First, there may be local edema, that is, if the foot is traumatized, it can cause local edema, because the blood vessels will be stretched after trauma, and the blood plasma or water liquid components will be extravasated to cause edema. Secondly, if the blood circulation of the feet is impaired, such as blockage of the blood vessels above the feet, it can cause edema of the blood vessels, especially a blockage of the venous vessels, which causes the blood in the feet not to flow back and stagnate in the blood vessels, thus causing edema. Thirdly, if the protein itself is low, it cannot fix the liquid component of the blood in the blood vessels, thus making the liquid leak out from the blood vessels to the tissues, resulting in edema.