You may be instructed to use some form of heat when the acute stages of healing are over, which is a minimum of two to three days. Heat makes blood vessels vasodilate (get larger). This action helps flush away chemicals that can cause pain. It also helps to bring in nutrients and oxygen, which help the area heal. True heat in the form of a moist hot pack, a heating pad, or warm shower or bath is more beneficial than creams that merely give the feeling of heat. Hot packs are usually placed on the sore area for 15 to 20 minutes. Special care must be taken to make sure your skin doesn't overheat and burn. It's also not a good idea to sleep with an electric hot pad at night. This can lead to the "lobster effect" where you can actually burn from the prolonged heat.