Thermal-Aid is a 100% natural therapeutic heating and cooling treatment pack. These packs were designed to reduce swelling and relieve pain. Thermal-Aid products are microwave safe and can be placed in your freezer. The heating/cooling agent is a specialized corn that holds temperatures for long periods of time. Thermal Aid has been tested on patients and animals with arthritis, fibromyalgia, broken bones, multiple sclerosis, migraines, backpain and various muscle aches.