Caldera's patent pending Pet Therapy Line is customized for canine anatomy. They've modified the gel formula in their pet line for prolonged effectiveness. All Caldera reusable Pet Therapy Gel is made in the USA and can be applied either hot or cold. Pet Therapy Gel is latex free, non-toxic, non-hazardous, microwave and freezer safe and remains pliable when frozen. Heating and freezing instructions are on each gel pack.