Narrowing the Blood Vessels
Ice works as a constricting agent, that narrows the blood vessels at the area of injury, thereby reducing blood flow to that region. Unfortunately, blood flow is a natural healing device used by the body to bring white blood cells to the site of the injury to begin the healing process. While ice can reduce swelling by restricting the amount of blood and other fluids that can reach the site, it can also slow down the healing process in this fashion. Therefore, ice should never be applied for an excessive length of time. A few minutes immediately after the injury and several times a day or whenever desired will do no harm, but never use ice for longer than ten minutes at a time. Ice can also cause the lymphatic system near the injury to open up and deluge the injured area with fluids that can actually contribute to the swelling and pain of the injury if left on the site too long. A shorter period of time on ice is best as the fat cells will hold in the lowered temperature for a period of time even after the ice has been removed. This is why your arm or leg still feels cold several minutes after you remove the ice.
Reducing Pain and Inflammation
Applying ice to an injury reduces pain and inflammation but if not done correctly it can actually injure the area more by creating an ice burn on the skin, which can break down the cellular structure of the skin. Always apply the ice on top of a cloth to protect the skin from further injury. The extreme cold should not be applied directly to the skin as it can cause more harm than good. Some ice packs come with a padded fabric sleeve that you slide the frozen pack into prior to use. Then you simply tie the pack around the injury or lay it atop the skin and the extreme cold is lessened somewhat by the layers of fabric. Most people have a pain threshold that is reached fairly quickly when ice is left directly on the skin for longer than just a few seconds.
Ten Minutes On, Thirty Minutes Off
Try using ice for ten minutes right after the injury occurs, then wait half an hour and ice it again for another ten minutes. Do this twice an hour for as long as needed and the swelling will go down, the skin will not be ice burned and the lymphatic system will do its job properly and remove fluids from the injury site. After a while you will notice that the swelling remains down between icings and that is a good sign that the ice has done its job and is no longer needed. Try to use the ice frugally as less is best when it comes to treating injuries with ice.