ThermaCare® was designed to provide heat therapy for long-lasting, powerful pain relief and muscle relaxation. It can be combined with a return to normal activities as recommended by current therapeutic guidelines. Because it's designed to be used anytime, anywhere, it wasn't possible to make it reusable. ThermaCare® works by using iron particles that, when exposed to air, will start reacting. This reaction gives off heat. Once the iron is used up, it cannot be reactivated or recharged. So once the product stops heating, it should be thrown away.