Edema, also known as oedema, refers to the accumulation of excessive fluid in the interstitial space of the body’s tissues, causing them to swell. Under normal circumstances, fluid in human blood vessels is constantly filtered out from the small capillary artery end to the tissue interstitial space to become tissue fluid, and tissue fluid is constantly absorbed back into the blood vessels from the small capillary vein end, maintaining a dynamic balance between the two, so that there is no excessive fluid accumulation in the tissue interstitial space. There are many causes of edema, which can be broadly classified into physiological causes, disease factors, allergic reactions, trauma, drug factors, etc. There are also some edema without clear causes. The clinical manifestations of edema include weight gain and subcutaneous swelling, which can be divided into systemic and localized, while subcutaneous edema is divided into depressed and non-depressed. When edema occurs in the body, it is necessary to restrict salt diet, eat more fresh vegetables and fruits, pay attention to rest, and give treatment for the primary disease, and some edema will be reduced or eliminated after the primary disease is controlled.