Vascular permeability is the ability of a substance to pass through the vessel wall. The vessel wall is made up of endothelial cells and basement membrane. These two have different permeabilities and can pass a number of different large and small molecules respectively. The endothelial cells can pass fluids and macromolecules, while the basement membrane can pass small molecules and block the entry of large molecules, such as proteins. If the permeability of blood vessels increases, large amounts of proteins will enter the tissue fluid, increasing the osmotic pressure of the tissue fluid and possibly causing edema. If the patient has symptoms such as edema, it is necessary to consult a doctor in time to avoid aggravating the symptoms and affecting the health of the body.