Heat application may be superficial or deep. The intensity and duration of the physiologic effects are determined mainly by tissue temperature, the rate of temperature elevation, and the area treated. Precautions must be taken to avoid burns. Hot packs are cotton cloth containers filled with silicate gel that are boiled in water, cooled, and applied to the skin. Wrapping the packs in several layers of towels helps protect the skin from burns.
Contraindications are the same as for infrared heat.
The method of application is dipping, immersing, and painting. The heat can be retained by wrapping the affected area with terry cloth for 20 min. A hand is easy to dip or immerse, whereas a knee or elbow is best treated by painting. Hydrotherapy may be used to enhance wound healing or to apply heat. Agitated warm water stimulates blood flow and debrides wounds.