When we incur minor injuries, we are often not sure of whether to use heat or ice as a means of first aid. The matter is made even more confusing by the fact that we are inundated by advertisements of over-the-counter products. There are basic ways to determine whether you should use heat or ice to treat a minor injury, and there are specific steps for effectively applying each option.
If you have or think you may have a major injury, stop poking around on the Internet for advice and call EMS. Do whatever they tell you to do until they arrive. Your health is worth way more than the cost of the service.
If you have a minor injury such as the result of falling and banging your knee or elbow into something, or if you have an injury due to overuse, such as running faster or farther than you were conditioned for, then follow these steps, with the first step being to immediately stop doing whatever it was that you were doing.
Ice is typically suggested for acute injuries, in an effort to reduce swelling and keep it down. This is often seen used on football players when they get knocked down unusually hard. You should ice the injury as quickly as possible after it occurs. The injured body part is likely to be reddish in color, and warm to the touch. It may also appear visibly inflamed. If it appears this way relative to its uninjured counterpart on the other side of your body, this means that ice is likely the recommended treatment.
Never apply ice directly on the skin, but you don't need an expensive fancy ice pack either. It is usually sufficient to use a bag of crushed ice, or even a bag of frozen peas, beans, or corn. While you want to ice the injury effectively, you also don't want to literally freeze it. Place a sheet or some other barrier between the bag and your skin. Wraps and bandages containing gel freezer packs are also available, but sometimes these can actually be so thick that you hardly feel the ice through them.
In any case, never ice an injury for longer than 20 minutes, as this can lead to frostbite. Wait about 45 minutes to an hour before icing again as needed, and don't use the injured body part during that time. Just be still.
Never apply ice proactively -- in other words, don't try to use it before you do something that you anticipate will cause an injury. It just doesn't work like that. You can, however, apply heat to loosen up a stiff joint before doing an activity.
Icing is typically only suggested for the first 48 hours after an injury occurs. Beyond that, it is usually considered to be ineffective. That is why you want to ice an injury and get the swelling down during that time frame.
After that 48-hour period, if all swelling is gone, heat can be applied to an injury to increase blood flow to the area and promote healing. Heat can also be used before an activity, which uses the effective body part, in order to loosen the area and remedy stiffness.
In short, the advice for heat application is essentially the opposite of ice. Never use heat after an acute injury, or after an injury due to overuse. Use ice for those purposes. Never use ice before an activity; but use heat on a critical joint before an activity.
Heat can be applied in many ways. Disposable, self-activating heating patches are available which provide many hours of heat. You can also use an electric heating pad, or a hot, wet towel. Moist heat can often be more effective than dry heat, but experiment with both. In any case, never use any heating device while you are sleeping or not attending to it. You need to ensure that you are not burning your skin. It is usually sufficient to just apply a small amount of heat for a small amount of time to have good results.
Don't get yourself into an endless cycle of using heat to loosen up a joint, then injuring it through overuse, and then icing it to bring down the swelling, only to repeat the same pattern the next day. If this sounds like something you do, consider taking six weeks off from the activity in question, and then building back up to it gradually and safely. Heating and icing should be a means of first aid, not a way of life.
Note that a minor injury should get noticeably better over a 72-hour period, especially if you are following these steps. If you see that this is not happening, you may have injured yourself more than you realized, or were willing to admit to yourself. Seek medical attention.
Also, think of injuries as a time for self-reflection. Was your injury truly an accident, or are you doing silly things and being reckless? Are you going for 10-mile jogs when you are really only in condition for 1-mile ones? Think about what you can do to prevent the same injury from occurring in the future.