From New World Encyclopedia
(Redirected from Warts)
Classification and external resources
Warts on the big toe
ICD-10 B07
ICD-9 078.1
DiseasesDB 28410
MedlinePlus 000885
eMedicine emerg/641 
MeSH D014860

A wart is generally a small, rough, abnormal growth (tumor), caused by a contagious viral infection of the skin (typically) or mucous membrane. They commonly infect the surface layer of the hands and feet, but may also occur on the face and genital areas, among other surfaces, such as inside the mouth (Brodsky 2006). Warts can be passed from person to person or from one area of a person's body to another part (Brodsky 2006), whether by direct physical contact or secondary contact with the shed skin of a wart (such as via a towel or floor) (Skinner and Frey 2005).

The viruses causing warts are classified as part of the group of DNA-based viruses known as human papillomaviruses (HPV). Warts are not cancerous, but some HPV strains are linked to cancer formation (Skinner and Frey 2005). Warts typically disappear after a few months but can last for years and can reoccur.

About seven to ten percent of the population has a problem with warts, particularly among children, women, and young adults (Skinner and Frey 2005). As with other infections, the prevention and spread of warts is tied to personal responsibility. Their spread can be lessened by such preventive actions as proper hygiene, avoiding nail biting, wearing shoes, keeping feet clean and dry, exhibiting care regarding shared items, keeping one's immune system healthy (good diet, avoiding stress, and, in the case of genital warts, recognition that spread is tied to promiscuous sexual relations (Skinner and Frey 2005).

Causal agent

Warts are caused by viruses of the human papillomavirus family of viruses. Papillomaviruses are a diverse group of non-enveloped, DNA-based viruses that infect the skin and mucous membranes of humans and a variety of animals, ranging from birds to manatees (Moreno-Lopez et al. 1984; Rector et al. 2004; Campo 2006). Over 100 different human papillomavirus (HPV) types have been identified. Some HPV types may cause warts, while others may cause a subclinical infection resulting in precancerous lesions. All HPVs are transmitted by skin-to-skin contact.

A group of about 30-40 HPVs is typically transmitted through sexual contact and infect the anogenital region. Some sexually transmitted HPVs may cause genital warts. However, other HPV types which may infect the genitals do not to cause any noticeable signs of infection.

Papillomaviruses replicate exclusively in body surface tissues such as the skin, or the mucosal surfaces of the genitals, anus, mouth, or airways (Doorbar 2005). Most papillomavirus types are adapted to infection of particular body surfaces. For example, HPV types one and two tend to infect the soles of the feet or the palms of the hands, respectively, where they may cause warts (de Villiers et al. 2004).

Types of warts

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 (Anderson et al. 1998). These include:

  • Common wart. A raised wart with roughened surface, most common on hands and face. Verruca vulgaris (hand warts) can grow anywhere on the hands, but often occur where skin is damaged, such as nail biting (Skinner and Frey 2005).
  • Flat wart (Verruca plana). A small, smooth flattened wart, tan or flesh colored, which can occur in large numbers; most common on the face, neck, hands, wrists and knees. Smoother and smaller than other warts (Skinner and Frey 2005).
  • Filiform or digitate wart: a thread- or finger-like wart, most common on the face, especially near the eyelids and lips . Usually found in multiples and most commonly seen in adult males, occurring in the bearded areas of the face or eyelids and neck (Skinner and Frey 2005).
  • Plantar wart (verruca, Verruca plantaris): a hard sometimes painful lump, often with multiple black specks in the center; usually found on pressure points on the soles of the feet. Also known as foot warts, they are the most painful types of warts and are commonly contracted in locker rooms and swimming pool areas, and thus common in children and young adults (Skinner and Frey 2005). They often resemble a cauliflower. The name plantar wart specifically describes HPV infection on the sole of the foot, but infection by the virus is possible anywhere on the body and common especially on the palm of the hand, where the appearance of the wart is often exactly as described for plantar warts.
  • Mosaic wart: a group of tightly clustered plantar-type warts, commonly on the hands or soles of the feet.
  • Genital wart (venereal wart, condylomata acuminatum, moist wart, Verruca acuminata): One of the most common sexually transmitted diseases and more contagious than other types of warts (Skinner and Frey 2005). Genital warts are the most easily recognized sign of genital HPV infection. Even when the genital warts are removed, the virus continues to live, and some strains of HPV can cause tissue changes in the cervix of women with cervical infection (Skinner and Frey 2005).


Many times warts do not need treatment, since many disappear spontaneously (67 percent over a period of two years), particularly in the case of flat warts (Skinner and Frey 2005).


Two viral warts on a middle finger, being treated with a mixture of acids (like salicylic acid) to remove them. A white precipitation forms on the area where the product was applied.

Treatments that may be prescribed by a medical professional include:

  • Keratolysis. Involves removal of dead surface skin cells, usually using salicylic acid, blistering agents, immune system modifiers ("immunomodulators"), or formaldehyde.
  • Cryosurgery. Involves freezing the wart (generally with liquid nitrogen), after which the wart and surrounding dead skin falls off by itself.
  • Surgical curettage. Involves use of a curette to remove tissue by scraping or scooping 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 (Horn et al. 2005).
  • Cantharidin. This is 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 percent observed with salicylic acid compared with 48 percent for placebo in six placebo-controlled trials including a total of 376 participants (Gibbs et al. 2003). 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 in many nations. 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.

Additional remedies

Aromatherapy treatments aim to kill the virus with an appropriate essential oil, such as onion and garlic oils, as well as tea tree oil (Skinner and Frey 2005). Herbal remedies include extracts of plants form the Euphorbia family, juice of a sour apple, fresh banana skin, juice of white cabbage, juice of the dandelion, and rubbing of a raw clove on the wart every night (Skinner and Frey 2005).

Other household remedies include the application of such common household items as a bruised garlic, 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, poison ivy, 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.

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. (2002) found that the duct tape method was 85 percent effective, compared to a 60 percent success rate in the study's cryotherapy group. Another study by Wenner et al. (2007), 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.

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 (IHL).

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.

ISBN links support NWE through referral fees

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  • Brodsky, R. 2006. Wart. In J. Longe, The Gale Encyclopedia of Medicine. Detroit: Thomson Gale. ISBN 1414403682.
  • Campo, M. S. (editor). 2006. Papillomavirus Research: From Natural History To Vaccines and Beyond. Caister Academic Press. ISBN 9781904455042.
  • de Villiers, E. M., C. Fauquet, T. R. Broker, H. U. Bernard, and H. zur Hausen. 2004. Classification of papillomaviruses. Virology 324(1): 17–27. PMID 15183049.
  • Doorbar, J. 2005. The papillomavirus life cycle. J. Clin. Virol. 32(Suppl 1): S7–15. PMID 15753007.
  • Focht, D. R., C. Spicer, and M. P. Fairchok. 2002. The efficacy of duct tape vs cryotherapy in the treatment of verruca vulgaris (the common wart) Archives of Pediatrics & Adolescent Medicine 156(10): 971-974. Retrieved March 9, 2008.
  • Gibbs, S. I. Harvey, J. C. Sterling, and R. Stark. 2003. Local treatments for cutaneous warts. Cochrane Database of Systematic Reviews Issue 3.
  • Horn, T. D., S. M. Johnson, R. M. Helm, and P. K. Roberson. 2005. Intralesional immunotherapy of warts with mumps, Candida, and Trichophyton skin test antigens Arch Dermatol 141: 589–594. Retrieved March 9, 2008.
  • Internet Health Library (IHL). n.d. Alternative and complementary therapies: Hypnotherapy & warts Internet Health Library. Retrieved March 9, 2008.
  • Moreno-Lopez, J., H. Ahola, A. Stenlund, A. Osterhaus, and U. Pettersson. 1984. Genome of an avian papillomavirus. J. Virol. 51(3): 872–875. PMID 6088809.
  • Rector, A., G. D. Bossart, S. J. Ghim, J. P. Sundberg, A. B. Jenson, and M. Van Ranst. 2004. Characterization of a novel close-to-root papillomavirus from a Florida manatee by using multiply primed rolling-circle amplification: Trichechus manatus latirostris papillomavirus type 1. J. Virol. 78(22): 12698–12702. PMID 15507660.
  • Skinner, P., and R. J. Frey. 2005. Wart. In J. Longe, The Gale Encyclopedia of Alternative Medicine. Farmington Hills, Mich: Thomson/Gale. ISBN 0787693960.
  • Wenner, R., S. K. Askari, P. M. Cham, D. A. Kedrowski, A. Liu, and E. M. Warshaw. 2007. Duct tape for the treatment of common warts in adults: a double-blind randomized controlled trial Arch Dermatol. 143(3): 309-313. Retrieved March 9, 2008.


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