Whether you can do hot compresses after a bruise depends on the time of the bruise. It is prohibited to do hot compresses within 24-48 hours after the injury, because the pathological basis of this period is that there is exudation from the injured tissues, and the increasing exudation will make the local swelling obvious. If the local swelling is high, it will affect the local blood flow, therefore, cold compresses are needed during this period. The principle of cold compress is to make the blood vessels spasm and contract, slow down the blood circulation, so that the local swelling is reduced. If the swelling of the limb is not too obvious after 24-48 hours after the injury, you can consider doing hot compress, because doing hot compress during this period can accelerate the blood circulation, promote the absorption of hematoma and promote the repair of tissue trauma.