We all know that heat and ice can be used to treat pain and injuries. But what do they actually do? And when should you use one rather than the other? This is a subject that causes confusion, partly because the answer isn’t always completely set in stone. But in certain situations, hot or cold treatments can have a beneficial effect on our bodies. Here’s a quick guide to the basics.
What ice does
When we hurt ourselves, blood from the injury can leak into our surrounding soft tissues. That’s why we come up in a bruise or swelling. Ice acts as a vasoconstrictor. It causes blood vessels to narrow, which reduces blood flow into the area around the injury. This can be useful if you’ve strained, torn or damaged a muscle or ligament, because it helps to restrict tissue-bleed, prevent further swelling and generally reduce pain and inflammation in the area. This also means you can keep the joint more mobile than it might be otherwise, which is why you often see injured footballers reaching for ice packs when they hobble off the pitch. Ice is also useful for encouraging recovery from surgery.
How to use it
Ice is usually most effective immediately after an injury, when the tissue damage is at its worst. For this reason it’s generally best applied over the first 24 to 48 hours. Use a bag of crushed ice from the freezer (or alternatively a bag of frozen vegetables), but make sure you wrap the bag in a damp cloth or tea towel before applying it to your skin. Don’t leave the ice pack on for too long, or you risk a cold burn (known as local tissue necrosis). Ten to 20 minutes at most should be sufficient.
What heat does
If you’ve read this far, you can probably guess what we’re going to say next! Where ice constricts the blood vessels, heat has the opposite effect: it makes them dilate. This lets the body deliver more blood to the area, which in turn can help the tissue-healing process. When could use this to your own advantage? Generally speaking, if you’re trying to treat things like stiffness, muscle spasms or pain that is ongoing (chronic). Heat packs can have a soothing effect on these tissues. They can also ease some of the symptoms associated with anxiety and stress, which in themselves make pain feel worse. It’s no accident that people want to jump in the bath to unwind after a stressful day.
How to use it
There are several ways to apply heat to your body. Wheat bags and heat pads can help to distribute the warmth evenly. Or you can use a deep heat cream, a hot water bottle – or that warm bath we just mentioned. Remember that you’re aiming for gentle heat, not boiling hot temperatures. Too high a temperature can result in a burn, or erythema ab igne (literally ‘redness from the fire’), where the skin becomes red and blotchy. Always follow the manufacturer’s instructions if you’re using heat pads. And be careful not to use heat on a new injury, because it could make the problem worse.