What Heat Does for Pain:
When heat is applied to the skin, it causes more blood to flow into the area. Heat affects the skin as well as the underlying tissues. How deeply these effects travel depends on what type of heat is used. For instance, a heating pad may only target the "shallow" tissues, while therapeutic ultrasound can penetrate into the deeper muscles.
How Heat Helps Pain:
When blood flow increases to an area, it brings along oxygen and nutrients that can help to speed healing. Heat helps to relax muscles, which can decrease some types of pain sensations. The sensation of heat on the skin also provides something called an analgesic effect: it alters the perception of pain so you don't hurt as much.
How to Use Heat for Pain:
Using heat at home can be as simple as plugging in a heating pad, or filling a hot water bottle. In fact, many heating products available on the market don't require a plug or water: single-use air-activated heating pads can be worn all day, and then thrown away. Some therapy clinics use paraffin wax dips, which, while somewhat messy, can be purchased for use at home. These are usually reserved for hands and feet (it's hard to "dip" your lower back). You can also target many areas at once with heat therapy by taking a warm bath, or stepping into a hot tub.
When to Use Heat for Pain:
Heat can be used to relieve pain caused by chronic conditions of the muscles and joints, such as:
*Arthritis
*Old sprains or strains
*Muscle spasms
*Muscle stiffness
Because heat has a pain-relieving effect when applied to the skin, it can be used for other chronic pain conditions as well. In fact, many people in our therapy clinic request heat for nerve pain conditions as well as back pain caused by disk problems. There is little research evidence to suggest that using heat improves these conditions; however, many of our patients still find it comforting.
When NOT to Use Heat for Pain:
Heat is best for injuries or conditions that are not in the acute phase. In other words, don't use heat on a fresh injury: you could increase swelling, which in some cases could increase your discomfort. In these cases, ice is a better choice. Also, you shouldn't apply heat over irritated skin or open wounds (including incisions that are still healing). Finally, people with cancer should not use heat to treat pain, as there is a chance of increased tumor growth.