As well, warts which have been present for a long time are sometimes difficult to treat. This is called cryotherapy. Podophyllin, a caustic plant resin is sometimes used in combination with LN2. After 4 to 6 hours, podophyllin must be thoroughly washed off . If left too long, or applied to healthy skin, it can cause painful burns.
Treatments usually have to be repeated on a regular basis , once or twice a week.
Podophyllin should not be used during pregnancy as it is absorbed and may cause fetal damage. The third possible treatment is burning with electrocautery or laser. It is important to complete treatment until all the warts have disappeared. As treatment is often long, it is unrealistic to abstain from sexual intercourse, but condoms should be used. Pap tests sometimes show signs of papilloma infection before the warts even appear.