How they work
Benefits of Hot + Cold Therapy
Temperature can have various effects on the body, and the benefits have been documented for years as it can be one of the easiest to access treatments. Easily administered therapies include a bag of frozen peas on a twisted ankle, or a hot water bottle to ease cramps. Hot and cold therapies can be effective for numerous conditions and are often quite affordable, however, the general public can often confuse which situations call for hot or cold, or sometimes both. Healthline suggests the general; rule of thumb is heat for muscle pain or stiffness, cold for acute injuries or pain with inflammation and swelling. 
In basic terms, heat therapy improves circulation and blood flow to the area where heat is administered, with even a small temperature increase soothing discomfort and improving muscle flexibility. Heat can relax and soothe muscles and heal damaged tissues. Think hot water bottles, a warm bath, heated pads, steamed towels – the temperature should be warm rather than hot, though. Too hot and it can cause discomfort or even burns. The therapy works well when used for extended periods, for example, minor stiffness or tension can be relieved within 15-20 minutes, with more moderate or severe pain needing longer-lasting periods between 30 minutes and two hours.
There are two “types” of heat therapy: dry and moist.
- Dry heat is “conducted heat therapy” and can come from heated pads, dry heating packs, and saunas.
- Moist heat is “convection heat” and comes from steamed towels, moist heating packs (like a Beloved Pack), or a hot bath.
Clinically, it has been shown that moist heat can penetrate deep tissue, preserving muscle strength and activity, faster than dry heat. For example, moist heat from steamed towels or a hot bath would be the best way to relieve muscle soreness from exercise. The study did show that dry heat had a similar, but lesser, effect. However, the same study found that the heat generated from moist procedures only lasts for 2 hours compared to the 8 hours from dry heat packs, meaning moist heat would have to be re-applied more frequently.  It is believed that moist heat is more effective in warming tissues than dry heat as water transfers heat quicker than air. Dry heat, however, improves expansion of blood capillaries (vessels) known as vasodilation, which allows more blood flow thus increase the supply of oxygen and nutrients, and elimination of carbon dioxide and metabolic waste.
The most common use of heat therapy is rehabilitation as it can increase the extensibility of collagen tissues, increase blood flow, reduce pain, relieve spasms, reduces inflammation, oedema and helps in the post-acute phase of healing. It is useful for muscle spasms, myalgia, fibromyalgia, contracture, bursitis. Moist heat can help drain abscesses faster. Heat therapy is particularly common in treating headaches and migraines, sufferers of which tend to have tight muscles in their neck and upper back and so heat applied to that area can reduce some of the tension.  Heat therapy is also commonly used as a natural way to treat moderate to painful (dysmenorrhea) menstrual cramps. A review of multiple scientific studies found there was suggestive evidence for the effectiveness of heat therapy for dysmenorrhea, including a reduction in pain compared to placebo therapy and analgesic drugs. 
A popular ingredient in to create a heat pack at home is rice; a DIY heat pack comparison ranked jasmine rice in the top three fillings. This was due to its pleasant scent, pleasant feel, and heat retention. 
Note that heat therapy should not be used if the area is bruised and/or swollen, or to an open wound. Heat therapy should be used with caution in people with conditions that leave them at higher risk of burns or other complications, including diabetes, dermatitis, vascular diseases, deep vein thrombosis and MS. People with heart disease or hypertension should consult a doctor before using heat therapy, and pregnant people should check before using saunas or hot tubs.
Cold therapy is also known as cryotherapy. It works by reducing blood flow to the area it is applied, which can significantly reduce inflammation and swelling especially in joints or tendons. Cold therapy can temporarily reduce nerve activity, which can relieve pain. Treatments can include applying ice packs or cold pads (often gels), coolant sprays, ice massage or immersion in ice baths. In medicine cryosurgery applies extremely low-temperature liquid to destroy abnormal or diseased tissue, often used to treat skin conditions.
At home, cryotherapy is often carried out using ice packs or instant packs where gel freezes when hit or shaken in an endothermic reaction lowering the temperature. The reduction in temperature reduces blood flow, which limits the volume of fluid pooling around the injury which can minimize swelling and bruising. Cold therapy can also numb nerve endings thus reducing pain receptor messages to the brain. Cold therapy is somewhat effective in the treatment of migraine, although how it works is unclear. It is believed the constriction of blood vessels and reduction of inflammation helps, with an analgesic effect on the nervous system. 
Cold therapy can be used as soon as possible within the PRICE protocol – protection, rest, ice, compression, and elevation. Ice should never be applied directly to the skin – cold or ice packs are usually held in a protective coating, but if the only source is ice then it should be wrapped in a cloth to protect the skin. Cold therapy should be used for short periods, several times a day. More than 20 minutes of application or using cold therapy too frequently may cause nerve, tissue, or skin damage. Those with sensory disorders should not use cold therapy without supervision from a healthcare provider, as they may not be able to feel damage caused by the extreme temperatures – for example diabetes which can result in nerve damage and lessened sensitivity. Cold therapy should not be used on stiff muscles or joints, or if the patient has poor circulation.
Whilst it is commonly used, there is little clinical evidence of the efficacy of cold therapy.
Choosing between hot or cold depends on the type of therapy required. We always advise that you seek a medical professionals advice on the best therapy to fit your needs.