A cooling vest is a piece of specially made clothing designed to lower or stabilize body temperature and make exposure to warm climates or environments more bearable. Cooling vests are used by many athletes, construction workers, and welders, as well as individuals with multiple sclerosis, hypohidrotic ectodermal dysplasia, or various types of sports injuries. Types Cooling vests range in weight from around 1 to 3.5 kg, depending on the model. While many subtypes do exist, cooling vests fall into one of 5 primary types: Evaporative cooling vests are typically submersed in water for around 3 – 5 minutes and lightly wrung out or blot dried. They are usually worn outside the clothing and as the water in the vest interacts with specially treated cooling crystals or other cooling agents, the water evaporates which then causes body temperature to be reduced. They are lightweight, easy to use, and no electricity is required, making them perfect for people on the move. They are also the most affordable form of cooling vest. Ice chilled cooling vests make use of cooling energy packs that are activated inside of a freezer and then placed in pockets inside of the cooling vest. Because they are very cold to the touch, this type of cooling vest is always worn outside the clothes. A phase change material (PCM) cooling vest makes use of cooling packs that maintain much higher temperatures when refrigerated, frozen, or placed in water. These phase-change packs often contain liquids (typically nontoxic oils and fats) that solidify (like wax) typically between 55 and 65 degrees and usually last between 1.5 – 4 hours. This flexible cooled pack will then help reduce the wearers' temperature for up to 4 hours. A cool flow cooling vest makes use of a water flow system that pumps water through the vest using hoses. A thermoelectric cooling vest works on Peltier effect and cools down the inner surface of the vest. It is powered by a portable battery. Uses The effects of cooling vests on athletes to improve their performance has been evaluated on several occasions; at the 2004 Summer Olympics several Americans and Australians were fitted with cooling vests supplied by Nike, used prior to their events. Cooling vests are also used by persons with multiple sclerosis. In multiple sclerosis, nerve fibers become demyelinated which leads to pain and discomfort when temperature is elevated. Nerve fibers may also be