Cryotherapy refers to “freezing.” Many patients equate this to “burning.” Cryotherapy involves applying a cryogen (i.e cold agent) which causes separation of the epidermis from the dermis, producing a blister. As the blister heals, the wart falls off. Typically, multiple sessions of freezing, spaced apart every 2 to 4 weeks, are required to produce clinical cure. Cryotherapy can be painful, produce temporary discoloration and, in rare circumstances, scarring. Home freezing kits containing propane and dimethyl ether (-70 °C) are sold over-the-counter. Home kits tend to be much less effective than liquid nitrogen (boiling point of -195°C) which produces more robust freezing.