Ice packs and heating pads are common household treatments. They’re affordable, and can often help with symptom relief quickly. But since both are used so often, it can become confusing to know when to use what. Here are some general guidelines to help you determine whether to use ice or heat on an injury.
Ice should be used for new or fresh injuries associated with swelling or pain. As a general rule, use ice if it’s been less than 48 hours since the injury occurred. Ice works by reducing blood flow to the area, which can reduce swelling and inflammation, especially if the injury involves a joint or a tendon. It’s also a low-grade analgesic, which means it helps numb up the area and soothe pain. Common injuries that benefit from ice include a twisted ankle or a pulled muscle.
In general, ice works less well than heat on muscles, unless the 48-hour rule applies: if it’s a new injury, ice will still help keep swelling down. For example, low back pain and neck pain may be worsened with ice, as can muscle spasms or stiff muscles. Never ice a chronic injury before activity or exercise, as this can actually increase the chance of re-injuring the area.
How to ice:
Never place ice directly on an injured area. Cover ice packs or a bag of ice cubes (or frozen peas) with a thin towel (it can be moistened with cold water if you don’t mind the dampness). Keep moving the ice pack around, and don’t ice for more than 30 minutes at a time.
Heat works great for chronic muscle and joint conditions. It opens up the blood vessels to improve blood flow, which can help relax and loosen tissues. This works great for aches and overuse injuries, especially before participating in activities or exercise.
It’s better not to use heat treatments after activity or right after an acute injury (think of the 48-hour rule again). Unlike ice, which reduces swelling, heat encourages blood and fluid to rush to the site. This can cause extra swelling (and extra pain) in new injuries.
How to heat:
Heating pads are affordable and readily available. In a bind, try moistening a towel with hot water, or popping it in the microwave and then wrapping it in another bag or thin towel. Be careful not to use hot objects, which can cause burns. You should aim for warm, moderate heat. Never use heating pads for more than two hours, and do not use them while sleeping or napping.
Your body knows itself. If extra ice or extra heat is causing discomfort, take a break and don’t force it. In addition, stress and fear are major contributors to pain and discomfort. The best thing you can do during an injury is to take a breather and try to rest and relax.
Do not use cold or heat packs:
Over areas of skin that are broken down or in poor condition, such as when there is rash/dermatitis, cuts, abrasions, or blisters
Over areas of skin that are numb or have poor temperature sensation—it’s easy to leave ice or heat on these areas for too long, which can cause injury
Over areas of skin with poor circulation, or if you have a history of blood clots
Over open wounds
Over areas of infection
If you have diabetes or diabetes-related nerve damage
Medical content edited by Mark Clark, MD, Medical Director, Block Island Medical Center.