Cold compresses should be applied within 24 hours after the collision because the injured area will bleed gradually within 24 hours after the collision, and the cold compresses can make the blood vessels contract and reduce bleeding, which will help a lot in the absorption of blood stasis in the later stage. If the collision after 48 hours, you can take the hot compress approach to deal with, because once the collision injury, in 48 hours after the general will not bleed, and has oozed out of the blood needs to be completely absorbed, in order to make the collision injury after the better. In order to absorb blood stasis, blood circulation must be accelerated, and hot compresses can accelerate blood circulation very well, which will help the absorption of blood stasis. In addition, after 48 hours after the collision, you can also use external blood circulation drugs or oral blood circulation drugs to accelerate the absorption of blood stasis.