Cryotherapy refers to a treatment in which surface skin lesions are frozen.
Cryogens used to freeze skin lesions include:
- Liquid nitrogen
- Carbon dioxide snow
- Dimethyl ether and propane or DMEP
Cryotherapy using liquid nitrogen (temperature –196C) involves the use of a cryospray, cryoprobe or a cotton-tipped applicator. The nitrogen is applied to the skin lesion for a few seconds, depending on the desired diameter and depth of freeze. The treatment is repeated in some cases, once thawing has completed. This is known as a ‘double freeze-thaw’ and is usually reserved for skin cancers or resistant viral warts.
Carbon dioxide snow
Carbon dioxide cryotherapy involves making a cylinder of frozen carbon dioxide snow (–78.5C) or a slush combined with acetone. It is applied directly to the skin lesion.
DMEP works at a temperature of –57C. It comes in an aerosol can available over the counter. It is used to treat warts using a foam applicator pushed onto the skin lesion for between 10 and 40 seconds, depending on its size and site.
Cryotherapy stings and may be painful, at the time and for a variable period afterwards. There may be immediate swelling and redness. This may be reduced by applying a topical steroid on a single occasion straight after freezing. Aspirin orally may also reduce the inflammation and discomfort.