Cryotherapy is often carried out by a healthcare practitioner at an out-patient consultation. The liquid nitrogen is usually applied to the skin by using a spray gun, a metal probe, or a cotton bud. Cryotherapy does not normally require a local anaesthetic as pain is usually mild and short lived (although this does vary between individuals and according to the body site being treated). The procedure itself lasts a matter of seconds; the precise time depends on the thickness and size of the lesion. The frozen skin becomes white and takes one to two minutes to thaw back to normal skin temperature. Your doctor may suggest that the process be repeated once the skin has thawed. Treatment is likely to produce a reaction similar to a burn. The skin may look red, swell, or blister. Redness may not be apparent in people with darker skin. After a few days, a scab will form, and this will take a few weeks to fall off depending on the site (occasionally a little longer, especially on the legs where healing is slow).