Plastic sheet can be heat-sealed to form a water-tight envelope havingan open top. A water-tight frangible container can be loaded into theenvelope through the open top. The water-tight frangible container cancontain a predetermined amount of water. A predetermined amount ofurea can be loaded into the envelope through the open top. Separatefrom the loading of the urea, a predetermined amount of ammoniumchloride can be loaded into the envelope through the open top. Therelative proportions of the predetermined amount of urea, thepredetermined amount of ammonium chloride, and the predeterminedamount of water can be selected to provide a target cooling effect toa portion of a body to which cooling is to be applied. The open top ofthe envelope can be heat-sealed to form a water-tight outer pack.
