Cryotherapy is a treatment using liquid nitrogen or nitrous oxide to freeze the skin. As the skin thaws out, the subsequent inflammation attracts the immune cells to the area, helping to fight the virus which causes verruca. The skin may also blister, which removes some of the infected skin, although this is not necessary for treatment to be successful.
Treatment is normally a course, with weekly or fortnightly visits. Unfortunately, as with all verruca treatment, a cure cannot be guaranteed. The freeze normally lasts between 30 seconds and a minute, and may be repeated. Because the freezing liquid is very cold, it can be uncomfortable during the treatment, feeling a bit like a burn, and can sometimes throb a few hours later. Painkillers can be taken, but not anti-inflammatories, as this could reduce the effectiveness of the inflammatory response.
This treatment is not recommended for people with circulation issues, diabetes, or very nervous patients.