Broadly defined these therapies use a spray to cool the area they are treating, the goal is usually to "trick" the nervous system by quickly cooling the skin. In our office we use a product called "instant ice" that contains two products that react with the air and when they hit the skin they create a strong feeling of cold. The 2 products are hydrocarbons and have not been found to cause any adverse reactions (for more information on product specifics feel free to contact the manufacture.) Instant ice evaporates almost instantly after contact so there is very little absorption compared to a product such as "Biofreeze". They have been effectively used in combination with trigger point therapies as well as used as a numbing agent prior to an injection.