Applying heat can relieve pain by relaxing the muscles, producing a sedative effect, and decreasing muscle tension. Ice can temporarily relieve pain almost any time.

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When it comes to chronic pain, many of us reach for heat or ice therapy, thinking one or the other will ease our symptoms. It’s easy to grab the heating pad or the ice pack, but both target symptoms, not underlying causes or long-term cures, and that can be a problem. That said, while you’re waiting to get in to see your doctor you can find temporary relief from heat or ice.

We’ll help you understand heat or ice therapy in detail, but here’s a great starting-point hint: Use ice if pain limits your motion, and use heat if stiffness limits your motion. (See also our post “Ice or Heat? For Back Pain, It Depends.”)

Heat

Heat applications, whether in the form of a heating pad or some other method of transferring heat to the body surface, increase the flow of blood, nutrients, and oxygen to affected areas of the body. Applying heat also can relieve pain by relaxing the muscles, producing a sedative effect, and decreasing muscle tension.

A Journal of Clinical Nursing study found that heat application every other day decreased pain and disability in patients with knee osteoarthritis. It also improved quality of life scores of physical function, pain, and general health perception of patients.

But it’s not necessarily your go-to choice. Heat, according to the journal Spine, is not an appropriate therapy for:

• Dermatitis
• Deep-vein thrombosis
• Diabetes
• Peripheral-vascular disease
• Open wounds
• Patients with severe cognitive impairment

Use heat for chronic pain whenever you think it will ease your pain, as long as you have your doctor’s permission and follow safety guidelines:

• Do not apply heat directly to the skin.
• Wrap heating devices in a thin towel.
• Do not apply heat for more than 20 minutes at a time (unless instructed to do so by your physician or physical therapist).
• Do not use heat on areas that are swollen.
• Do not use heat on open wounds or stitches.
• Do not lie down on a heating pad.

(Adapted from the University of Rochester Medical Center Health Encyclopedia)

Wet heat can be more effective because it penetrates deeper than dry heat. A hydrocollator is a heating pad that applies moist heat to superficial and subcutaneous (just below the surface) tissues. Other methods of applying heat are baths, showers, hot tubs, and whirlpools using warm water between 92° and 100° F.

Cold

Applying an ice pack, chemical cold pack, or a cooling therapy system to an area of the body that is hurting is a temporary solution to a long-term problem. But it works, at least for a while, and many chronic-pain patients will settle for that until they find a longer-lasting remedy.

Cold decreases temperature, inflammation, rate of metabolic activity, circulation, muscle spasms, and pain. It shrinks blood vessels and, in doing so, minimizes bleeding and swelling. In medical terms, cryotherapy helps with pain because it reduces nerve end sensitivity. In lay terms, ice deadens the pain in that area.

Using Cold Therapy Safely

If you have aggravated an old injury, the general rule is to use ice for the first 48 to 72 hours or until the swelling subsides. At first, the ice will feel uncomfortably cold. Then you’ll feel a burning sensation, followed by an aching feeling, and finally, numbness. Ice can temporarily relieve pain almost any time.

Apply ice for 10- to 30-minute periods, separated by at least an hour between applications. The duration of applications also should vary with the area of the body being iced. Tissues, muscles, and structures that lie close to the surface of the skin or have little surrounding body fat require less icing time than those that lie deeper in the body.

Guidelines for Using Heat or Ice