A wart is generally a small, rough tumor, typically on hands and feet, that can resemble a cauliflower or a solid blister. Warts are common, and are caused by a viral infection, specifically by the human papillomavirus (HPV) and are contagious when in contact with the skin of another. It is also possible to get warts from using towels or other objects. They typically disappear after a few months but can last for years and can reoccur. A few papilloma viruses are known to cause cervical cancer.
Types of wart
A range of different types of wart have been identified, which differ in shape and site affected, as well as the type of human papillomavirus involved. These include:
- common wart (Verruca vulgaris): a raised wart with roughened surface, most common on hands and knees
- flat wart (Verruca plana): a small, smooth flattened wart, tan or flesh coloured, which can occur in large numbers; most common on the face, neck, hands, wrists and knees
- filiform or digitate wart: a thread- or finger-like wart, most common on the face, especially near the eyelids and lips
- plantar wart (verruca, Verruca pedis): a hard sometimes painful lump, often with multiple black specks in the center; usually only found on pressure points on the soles of the feet
- mosaic wart: a group of tightly clustered plantar-type warts, commonly on the hands or soles of the feet
- donkey wart (venereal wart, Condyloma acuminatum, Verruca acuminata):
Treatments that may be prescribed by a medical professional include:
- Keratolysis, removal of dead surface skin cells usually using salicylic acid, blistering agents, immune system modifiers ("immunomodulators"), or formaldehyde.
- Cryosurgery, which involves freezing the wart (generally with liquid nitrogen), after which the wart and surrounding dead skin falls off by itself.
- Surgical curettage of the wart.
- Laser treatment.
- Imiquimod, a topical cream that helps the body's immune system fight the wart virus by encouraging interferon production.
- Candida injections at the site of the wart, which also stimulate the body's immune system.
- Cantharidin, a chemical found naturally in many members of the beetle family Meloidae which causes dermal blistering.
The wart often regrows after the skin has healed.
One review of 52 clinical trials of various cutaneous wart treatments concluded that topical treatments containing salicylic acid were the best supported, with an average cure rate of 75% observed with salicylic acid compared with 48% for placebo in six placebo-controlled trials including a total of 376 participants. The reviewers also concluded that there was little evidence of a significant benefit of Cryotherapy over placebo or no treatment.
There are several over-the-counter options. The most common ones involve salicylic acid. These products are readily available at drugstores and supermarkets. There are typically two types of products: adhesive pads treated with salicylic acid or a bottle of concentrated salicylic acid solution. Removing a wart with salicylic acid requires a strict regimen of cleaning the area, applying the acid, and removing the dead skin with a pumice stone or emery board. It may take up to 12 weeks to remove a wart.
Another over-the-counter product that can aid in wart removal is silver nitrate in the form of a caustic pencil, which is also available at drug stores. This method generally takes three to six daily treatments to be effective. The instructions must be followed to minimize staining of skin and clothing.
Over-the-counter cryosurgery kits are also available, however they can often cost three times as much as the previously named products.
Like prescription treatments, over-the-counter treatments usually require multiple applications and are only necessary if the warts are problematic. Additionally, these treatments are capable of destroying healthy skin as well as warts, so caution must be exercised by those attempting them without medical supervision.
Duct tape occlusion therapy involves placing a piece of duct tape (or medical tape) over the affected area for a week at a time. The procedure is otherwise identical to that of using salicylic acid adhesive pads. One study by Focht et al. found that the duct tape method was 85% effective, compared to a 60% success rate in the study's cryotherapy group. Another study by Wenner and coworkers, however, found no statistically significant effect in a double-blind, randomized and controlled clinical trial in 90 adults when duct tape was compared to mole skin. There was no statistically significant difference for resolution of the target wart between patients treated with moleskin versus patients treated with duct tape. Eight of 39 patients [21%] in the treatment group vs 9 of 41 patients in the control group [22%] had complete resolution of the target wart. Fewer of the patients achieving resolution of their wart in the moleskin group had recurrence of their wart. Of the patients who had complete resolution, 6 (75%) in the treatment group and 3 (33%) in the control group had recurrence of the target wart by the sixth month. "Whether or not the standard type of duct tape is effective is up in the air," said co-author Dr. Rachel Wenner of the University of Minnesota, who started the new study as a medical student. "Theoretically, the rubber adhesive could somehow stimulate the immune system or irritate the skin in a different manner."
Other household remedies include the application of common household items. These include various fruits and vegetables such as a bruised garlic, banana skin, unskinned potatoes, potato or cauliflower or tomato juice, or other food products like vinegar, salt, or vegemite. Other common household products used include hot water and washing liquid, aerosol sprays or compressed air, and tempera paint. Oils and saps from milkweed, dandelion, and poison ivy, tea tree, Thuja occidentalis, and fig trees have also been used. Accounts vary in regards to how long these remedies must be applied with each session and how long they take to work.
As there have been no controlled studies for most household remedies, it is impossible to know if warts that disappear after such treatments do so because the treatment was effective, or because warts often disappear due to the individual's own immune system regardless of treatment. The evidence that hypnosis may effectively treat warts  suggests that the condition may be amenable to the placebo effect, that is, that belief in a remedy rather than any property of the remedy itself is what's effective.
Some household remedies are potentially dangerous. These include attempts to cut or burn away the warts. Incense is sometimes used in Asian countries to burn warts. These methods are very painful, and can lead to infection and/or permanent scarring.