The bruise is the situation when some blood vessels rupture, the red blood cells penetrate from inside the blood vessels to outside the blood vessels, and the iron in the red blood cells will form iron-containing hemoglobin, and the bruise becomes yellow. The most effective way to make the bruise yellow fade quickly is to apply local heat, because after local heat, the skin temperature increases, the blood flow speed is accelerated, it can promote the metabolism of iron-containing hemoglobin, thus promoting the bruise yellow fade quickly. Clinically, bruising can be caused by a variety of reasons, such as capillary rupture caused by trauma, increased capillary permeability caused by vitamin C deficiency, as well as thrombocytopenic diseases and various coagulation dysfunctional diseases, all of which can result in subcutaneous bruising. When subcutaneous bruising occurs, red blood cells penetrate outside the blood vessels and iron-containing heme will be formed, resulting in the bruise turning yellow, so the most effective way to turn the bruise yellow is to apply local heat.