Hot and cold packs can help relieve pain. The choice can depend on the type and cause of the pain.
Basic heat therapy, or thermotherapy can involve the use of a hot water bottle, pads that can be heated in a microwave, or a warm bath.
For cold therapy, or cryotherapy, a water bottle filled with cold water, a pad cooled in the freezer, or cool water can be used.
In some cases, alternating heat and cold may help, as it will greatly increase bloodflow to the injury site.
- Cold treatment reduces inflammation by decreasing blood flow. Apply within 48 hours after an injury.
- Heat treatment promotes blood flow and helps muscles relax. Use for chronic pain.
- Alternating heat and cold may help reduce exercise-induced muscle pain.
- Never use extreme heat, and never put ice directly on the skin.
Here are some key points about cold and heat treatment. More detail is in the main article.
Cold treatment reduces blood flow to an injured area. This slows the rate of inflammation and reduces the risk of swelling and tissue damage.
It also numbs sore tissues, acting as a local anesthetic, and slows down the pain messages being transmitted to the brain.
Ice can help treat a swollen and inflamed joint or muscle. It is most effective within 48 hours of an injury.
Rest, ice, compression and elevation (RICE) are part of the standard treatment for sports injuries.
Note that ice should not normally be applied directly to the skin.
Types of cold therapy
Some ways of using cold therapy include:
- a cold compress or a chemical cold pack applied to the inflamed area for 20 minutes, every 4 to 6 hours, for 3 days
- immersion or soaking in cold, but not freezing, water
- massaging the area with an ice cube or an ice pack in a circular motion from two to five times a day, for a maximum of 5 minutes, to avoid an ice burn
In the case of an ice massage, ice can be applied directly to the skin, because it does not stay in one place.
Ice should not be applied directly to the bony portions of the spinal column.
A cold compress can be made by filling a plastic bag with frozen vegetables or ice and wrapping it in a dry cloth.
What is ice useful for?
A cold compress applied within 48 hours of an injury can help reduce inflammation.
Cold treatment can help in cases of:
- a recent injury
- tendinitis, or irritation in the tendons following activity
A cold mask or wrap around the forehead may help reduce the pain of a migraine.
For osteoarthritis, patients are advised to use an ice massage or apply a cold pad 10 minutes on and 10 minutes off.
When not to use ice
Cold is not suitable if:
- there is a risk of cramping, as cold can make this worse
- the person is already cold or the area is already numb
- there is an open wound or blistered skin
- the person has some kind of vascular disease or injury, or sympathetic dysfunction, in which a nerve disorder affects blood flow
- the person is hypersensitive to cold
Ice should not be used immediately before activity.
It should not be applied directly to the skin, as this can freeze and damage body tissues, possibly leading to frostbite.
Professional athletes may use ice massage, cold water immersion, and whole-body cryotherapy chambers to reduce exercise-induced muscle damage (EIMD) that can lead to delayed onset muscle soreness (DOMS). DOMS commonly emerges 24 to 48 hours after exercise.
A study published in The Cochrane Library in 2012 suggested that a cold bath after exercise may help prevent DOMS, compared with resting or doing nothing.
The participants spent between 5 and 24 minutes in water between 50 and 59 degrees Fahrenheit, or 10 to 15 degrees Celsius.
However, the researchers were not certain whether there may be negative side effects, or if another strategy might be more helpful.
Cryotherapy is primarily a pain-reliever. It will not repair tissues.
Ice and back pain
Ice is best used on recent injuries, especially where heat is being generated.
It may be less helpful for back pain, possibly because the injury is not new, or because the problem tissue, if it is inflamed, lies deep beneath other tissues and far from the cold press.
Back pain is often due to increased muscle tension, which can be aggravated by cold treatments.
For back pain, heat treatment might be a better option.
Applying heat to an inflamed area will dilate the blood vessels, promote blood flow, and help sore and tightened muscles relax.
Improved circulation can help eliminate the buildup of lactic acid waste occurs after some types of exercise. Heat is also psychologically reassuring, which can enhance its analgesic properties.
Heat therapy is usually more effective than cold at treating chronic muscle pain or sore joints caused by arthritis.
Types of heat therapy
Types of heat therapy include:
- applying an electrical heating pad, hot water bottle, hot compress, or heat wrap
- soaking the area in a hot bath, between 92 and 100 degrees Fahrenheit or 33 and 37.7 degrees Celsius
- using heated paraffin wax treatment
- medications such as rubs or patches containing capsicum
Heat packs can be dry or moist. Dry heat can be applied for up to 8 hours, while moist heat can be applied for 2 hours. Moist heat is believed to act more quickly.
Heat should normally be applied to the area for 20 minutes, up to three times a day, unless otherwise indicated.
Single-use wraps, dry wraps, and patches can sometimes be used continuously for up to 8 hours.
What is heat useful for?
Heat is useful for relieving:
A hot bath can provide comfort and relief from some types of pain.
- strains and sprains
- tendonitis, or chronic irritation and stiffness in the tendons
- warming up stiff muscles or tissue before activity
- relieving pain or spasms relating to neck or back injury, including the lower back
In 2006, a team of researchers found that patients with lower back pain who exercised and use continuous low-level heat wrap therapy (CLHT) experienced less pain than those who did not use CLHT.
Previous studies had shown that, for some people, CLHT relieved pain more effectively than oral analgesics, acetaminophen, and ibuprofen.
However, the effectiveness of heat treatment may depend on the depth of the tissue affected by the pain or injury.
Some people use heat treatment, often in the form of a hot bath, to stave off DOMS.
There is some evidence that this might help, but heat that is applied for only 5 to 20 minutes may be less effective, as does not have the chance impact the deeper levels of tissue.
Some researchers have suggested that moist chemical heat packs, which can be used for 2 hours, may be the best way to prevent DOMS through heat treatment.
When not to use heat
Heat is not suitable for all injury types. Any injury that is already hot will not benefit from further warming. These include infections, burns, or fresh injuries.
Heat should not be used if:
- the skin is hot, red or inflamed
- the person has dermatitis or an open wound
- the area is numb
- the person may be insensitive to heat due to peripheral neuropathy or a similar condition
Excessive heat must be avoided.
Alternating cold and heat
When cold is applied to the body, the blood vessels contract, vasoconstriction occurs. This means that circulation is reduced, and pain decreases.
Removing the cold causes vasodilation, as the veins expand to overcompensate.
As the blood vessels expand, circulation improves, and the incoming flow of blood brings nutrients to help the injured tissues heal.
Alternating heat and cold can be useful for:
Contrast water therapy (CWT) uses both heat and cold to treat pain. Studies show that it is more effective at reducing EIMD and preventing DOMS than doing nothing.
A review of studies has suggested that, for elite athletes, CWT is better at reducing muscle pain after exercise compared with doing nothing or resting.
However, the researchers point out that it may not better than other strategies, such as heat treatment, cold treatment, stretching, or compression. They say that more evidence is necessary.
Tips and cautions
Heat should not be used on a new injury, an open wound, or if the person is already overheated. The temperature should be comfortable. It should not burn.
Ice should not be used if a person is already cold. Applying ice to tense or stiff muscles in the back or neck may make the pain worse.
Heat and cold treatment may not be suitable for people with diabetic neuropathy or another condition that reduces sensations of hot or cold, such as Raynaud's syndrome, or if they are very young or old, or have cognitive or communication difficulties.
It may be hard to know when the heat or cold is excessive in these cases.
Science has yet to firmly establish the effectiveness of heat and cold therapies, but neither treatment is very potent, and the danger of an adverse reaction, when applied to a particular point on the body, is usually low.
Individuals with chronic pain or a non-serious injury can try either method and find their own best solution.