Both heat and cold can help relieve pain, the choice between them depending on the nature and cause of the pain.
“A rule of thumb is that cold eases acute pain and heat eases chronic pain, such as from rheumatic illnesses,” says Andreas Kiefer, of the Federal Union of German Associations of Pharmacists.
Sport injuries such as contusions, sprains or pulled muscles should be cooled as soon as possible. Cold also helps in cases of acute inflammation, for example after an insect bite. Cooling can be done with running water, ice cubes, cold compresses or a cold spray.
“Never take cold compresses directly from a refrigerator and put them on the skin, though. This could cause hypothermia, particularly in joints. It's always better to put a thin cloth in between,” Kiefer advises. If the compresses are too cold and then removed, blood flow greatly increases and the pain intensifies.
“If a sport injury doesn't get better in three days or the function of a joint is restricted, a medical examination is definitely called for,” Kiefer says.
Heat also helps to alleviate pain. It makes tendons and ligaments more flexible, and it makes rheumatic joints more mobile. It also eases muscle tension. Heat promotes blood flow; consequently, more nutrients are delivered to tissues and waste products are carried away more quickly.
Heat can be effective in relieving menstrual cramps as well.
Simply soaking in a hot bath or placing a hot water bottle or heating pad on the lower abdomen is often sufficient. Vasodilating ointments and heat patches have the advantage of not restricting mobility, so they can be used at the workplace.
Someone suffering from an acute inflammation or fever should not apply heat, however. And people with venous or circulatory problems should see a doctor.
