Author: Dr Roy Palmer
Viral warts are caused by the human papilloma virus. They are common, particularly in children. If left untreated, the immune system usually eventually attacks warts, resulting in cure. In previous times, this encouraged faith in magical treatments, like touching a toad.
Because warts are infectious, patients should not share towels with others. Patients should try to avoid biting their nails, because this spreads warts around the edges of nails and to the skin around the mouth. Warts on the soles of the feet are known as verrucae. They can be acquired from the floors of showers and swimming pools, because the rough surfaces remove the outer layer of skin from moist infected feet, and implant the virus into the moistened skin of others.
Raised warts on the hands are known as common warts. Approximately 50% of these spontaneously resolve within one year. If treatment is required, first-line is usually topical salicylic acid. There are many preparations available without prescription, containing between 12 and 26% salicylic acid eg. Bazuka Extra Strength. Some also contain lactic acid eg. Salactol. Topical treatment requires motivation and persistence. The daily use of salicylic acid for 12 weeks is reported to cure two-thirds of patients with hand warts. Due to its irritancy, salicylic acid should not be applied to sensitive areas, such as the face. Most of the preparations are in a collodion base that dries to leave a whitish deposit; in other cases, a plaster should be applied afterwards.
If there is no improvement after 3 months, or if daily application is not in practice possible, then cryotherapy with liquid nitrogen is often considered. The application of cryotherapy is painful. For optimum effect, it should be repeated at relatively short intervals (every 2 to 3 weeks). It can be combined with treatment with salicylic acid.
For verrucae, pain is a common symptom. Without treatment their duration varies, being relatively short in young children but long in older children and adults, sometimes persisting for several years. As with common warts, first-line treatment is usually topical salicylic acid; a high concentration (eg. 50%) is best, but application is fiddly because the normal skin has to be protected from it. Cryotherapy is often used; it usually has to be given on multiple occasions, and it can be combined with eg. 50% salicylic acid treatment. Alternatively, application of a substance called cantharone causes blistering, which can be very severe, but it sometimes achieves cure when other treatments have failed.
Plane warts are nearly flat. They mostly occur on the hands and face, and can be very persistent; facial lesions cause the most distress. Warts on the genitals or around the anus are usually (but not always) sexually transmitted, and they are usually treated at a sexual health clinic.
Surgery can be useful for solitary lesions, particularly those on the face. Laser treatment can be curative but often is not. The limitations of the treatments described above has resulted in a long list of other therapies that are sometimes employed, which include gluteraldehyde, formaldehyde gel, podophyllin, 5-FU, and silver nitrate.