This leaflet gives a general overview of ice and heat therapy for soft tissue injuries and other pains. If you are uncertain about the use of heat or ice, consult a health professional such as a doctor, nurse or physiotherapist.
Why do we use ice and heat therapy?
Ice and heat therapy have been used for many years to treat pain and reduce swelling, and many people have found them effective. More recently, studies have been done to investigate whether ice or heat really makes a difference in healing, and the results have been inconclusive. In general, when used sensibly, they are safe treatments which make people feel better and have some effect on pain levels and there are few harms associated with their use.
How does heat reduce pain?
Heat is an effective and safe treatment for most aches and pains. Heat can be applied in the form of a wheat bag, heating pads, deep heat cream, hot water bottle or heat lamp.
Heat causes the blood vessels to open wide (dilate). This brings more blood into the area to stimulate healing of damaged tissues. It has a direct soothing effect and helps to relieve pain and spasm. It can also ease stiffness by making the tissues more supple.
If heat is applied to the skin it should not be hot; gentle warmth will be enough. If excessive heat is applied there is a risk of burns and scalds. A towel can be placed between the heat source and the skin for protection. The skin must be checked at regular intervals.
Heat should not be used on a new injury. It will increase bleeding under the skin around the injured area and may make the problem worse. The exception to this is new-onset low back strains. A lot of the pain in this case is caused by muscle spasms rather than tissue damage, so heat is often helpful. A large-scale study suggested that heat treatment had a small helpful effect on how long pain and other symptoms go on for in short-term back pain. This effect was greater when heat treatment was combined with exercise.
Heat is often helpful for the following types of pain:
- Aching muscles from over-exertion.
- Aching pains from fibromyalgia and other chronic pain conditions.
- Cramping or spasm pains such as period pains.
How does ice reduce pain?
Ice has traditionally been used to treat soft tissue injuries where there is swelling. However, there is a growing body of evidence which suggests that applying ice packs to most injuries does not contribute to recovery. It may even mean injuries take longer to discover. This is related to the fact that reducing the temperature at the site of an injury will delay the body's immune system response. It is the action of the immune system which will heal the injury.
In one study, some people who used ice said that it was helpful for managing pain, although this did not translate into a lower use of painkillers. Many people find that ice is helpful when used to manage pain in the short term. It is unlikely that it will have much of a negative effect in the long term when used in this way.
A review of studies into the effectiveness of ice treatment found that most studies were inconclusive and others showed only a small effect. Some of the recent results are listed below:
- A review of studies using ice and heat therapy for osteoarthritis of the knee found that ice packs reduced swelling and that ice massage improved muscle strength and range of movement. Heat packs had no effect on pain and swelling. No side-effects were reported to either heat or ice.
- A study of people using ice therapy for gout found that it made some improvement to their pain but it did not reduce swelling.
- Studies looking at the healing of stitches and tears following vaginal delivery of a baby found that cold gel packs and ice packs helped to relieve pain in some women.
- Studies which looked at a variety of treatments for neck pain found that neither heat nor cold was effective.
- There was some evidence that ice plus exercise was effective for ankle sprains.
- Ice can also be helpful to reduce swelling of surgical wounds.
With any sprain, strain or bruise there is some bleeding into the underlying tissues. This causes swelling and pain. Ice treatment may be used in both the immediate treatment of soft tissue injuries and in later rehabilitation.
During immediate treatment, the aim is to limit the body's response to injury. Ice will:
- Reduce bleeding into the tissues.
- Prevent or reduce swelling (inflammation).
- Reduce muscle pain and spasm.
- Reduce pain by numbing the area and by limiting the effects of swelling.
These effects all help to prevent the area from becoming stiff, by reducing excess tissue fluid that gathers as a result of injury and inflammation.
In the later, or rehabilitation, phase of recovery the aim changes to restoring normal function. At this stage the effects of ice can enhance other treatments, such as exercise, by reducing pain and muscle spasm. This then allows better movement. If you are doing exercises as part of your treatment, it can be useful to apply an ice pack before exercise. This is so that after the ice pack is removed the area will still be a little numb. The exercises can also be done with the ice pack in place. This reduces pain and makes movement around the injury more comfortable, although it can also make the muscles being exercised stiffer.
How do you make ice packs?
Ice packs can be made from ice cubes in a plastic bag or wet tea towel. A packet of frozen peas is also ideal. These mould nicely and can go in and out of the freezer. However, frozen vegetables should not be eaten if they have been thawed and re-frozen. Purpose-made cold packs can also be bought from pharmacies. Take care when using ice and cold packs from a deep freeze, as they can cause ice burns quickly if used without care and proper protection.
How are ice packs used?
- Ideally, rub a small amount of oil over the area where the ice pack is to go (any oil can be used, even cooking oil). If the skin is broken or there are stitches in place, do not cover in oil but protect the area with a plastic bag. This will stop the open wound from getting wet.
- Place a cold wet flannel over the oil (you do not need to if using a plastic bag).
- Place the ice pack over the flannel.
- Check the colour of the skin after five minutes. If it is bright pink or red remove the pack. If it is not pink, replace the bag for a further 5-10 minutes.
- Ice can be left on for 20-30 minutes but there is little benefit to be gained by leaving it on for longer. You run the risk of damaging the skin if ice is left on the skin for more than 20-30 minutes at a time. Leaving the ice on for too long can also slow down the healing process.
- The effect of the ice pack is thought to be improved if it is pressed gently on to the injured area.
Note: ice can burn or cause frostbite if the skin is not protected with oil or other protection such as a wet flannel.
How long should ice be applied for?
Ideally, ice should be applied within 5-10 minutes of injury and for 20-30 minutes. This can be repeated every 2-3 hours or so whilst you are awake for the next 24-48 hours.
After the first 48 hours, when bleeding should have stopped, the aim of treatment changes from restricting bleeding and swelling to getting the tissues remobilised with exercise and stretching. Ice helps with pain relief and relaxation of muscle tissue.
What precautions should I take when using ice and heat therapy?
Do not use heat or cold packs:
- Over areas of skin that are in poor condition.
- Over areas of skin with poor sensation to heat or cold.
- Over areas of the body with known poor circulation.
- If you have diabetes.
- In the presence of infection.
Also, do not use ice packs on the left shoulder if you have a heart condition. Do not use ice packs around the front or side of the neck.
Ice causes a longer-lasting effect on the circulation than heat,. Also, the painkilling properties of ice are deeper and longer-lasting than heat.
Both heat and ice can be re-applied after an hour if needed.
Further reading and references
Wang Y, Lu H, Li S, et al; Effect of cold and heat therapies on pain relief in patients with delayed onset muscle soreness: A network meta-analysis. J Rehabil Med. 2022 Feb 854:jrm00258. doi: 10.2340/jrm.v53.331.
Wilke J, Behringer M; Is "Delayed Onset Muscle Soreness" a False Friend? The Potential Implication of the Fascial Connective Tissue in Post-Exercise Discomfort. Int J Mol Sci. 2021 Aug 3122(17). pii: ijms22179482. doi: 10.3390/ijms22179482.
Garcia C, Karri J, Zacharias NA, et al; Use of Cryotherapy for Managing Chronic Pain: An Evidence-Based Narrative. Pain Ther. 2021 Jun10(1):81-100. doi: 10.1007/s40122-020-00225-w. Epub 2020 Dec 14.
Bleakley C, McDonough S, MacAuley D; The use of ice in the treatment of acute soft-tissue injury: a systematic review of randomized controlled trials. Am J Sports Med. 2004 Jan-Feb32(1):251-61.
Petrofsky JS, Laymon M, Lee H; Effect of heat and cold on tendon flexibility and force to flex the human knee. Med Sci Monit. 2013 Aug 1219:661-7. doi: 10.12659/MSM.889145.
French SD, Cameron M, Walker BF, et al; A Cochrane review of superficial heat or cold for low back pain. Spine (Phila Pa 1976). 2006 Apr 2031(9):998-1006.
Mayer JM, Ralph L, Look M, et al; Treating acute low back pain with continuous low-level heat wrap therapy and/or exercise: a randomized controlled trial. Spine J. 2005 Jul-Aug5(4):395-403.
Brosseau L, Yonge KA, Robinson V, et al; Thermotherapy for treatment of osteoarthritis. Cochrane Database Syst Rev. 2003(4):CD004522.