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THE MERCK MANUAL MEDICAL LIBRARY: The Merck Manual of Medical Information--Home Edition
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Warts

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Warts (verrucae) are small skin growths caused by any of 100 or more related human papillomaviruses.

  • Raised or flat growths appear on any part of the skin.
  • Most warts are painless.
  • Doctors identify warts by sight or rarely do a biopsy.
  • Warts that do not go away by themselves can be removed with chemicals or frozen, burned, or cut off.

Warts can develop at any age but are most common among children and least common among older people. People may have one or two warts or hundreds. Because prolonged or repeated contact is necessary for the virus to spread, warts are most often spread from one area of the body to another, but they can spread also from one person to another. Sexual contact is often sufficient to spread genital warts (see Sexually Transmitted Diseases: Genital Warts).

Most warts are harmless, although they may be quite bothersome. The exceptions are certain types of genital warts that sometimes cause cervical cancer in women.

Symptoms

Warts are classified by their location and shape. Some warts grow in clusters (mosaic warts), but others appear as isolated, single growths. Warts are painless, except for plantar warts.

Common Warts: Common warts (also called verrucae vulgaris), which almost everyone gets, are firm growths that usually have a rough surface. They are round or irregularly shaped; are gray, yellow, or brown; and are usually less than ½ inch (about 1 centimeter) across. Generally, they appear on areas that are frequently injured, such as the knees, face, fingers, elbows, and around the nails (periungual warts). Common warts may spread to surrounding skin.

Plantar Warts: These warts develop on the sole of the foot, where they are usually flattened by the pressure of walking and are surrounded by thickened skin. They tend to be hard and flat, with a rough surface and well-defined boundaries. They can be very painful when standing or walking, which puts pressure on the warts. Warts may appear on the top of the foot or on the toes, where they are usually raised and fleshier. Warts are often gray or brown and have a small black center. Unlike corns and calluses, plantar warts tend to bleed from many tiny spots, like pinpoints, when a doctor shaves or cuts the surface away with a knife. There can also be clusters of smaller warts, called mosaic warts.

Periungual Warts: Periungual warts are thickened, cauliflower-like growths around the nails (see Nail Disorders: Verruca Vulgaris). The nail may lose its cuticle, and other skin infections can develop around the nail. These warts are more common among people who bite their nails.

Filiform Warts: These warts are long, narrow, small growths that usually appear on the eyelids, face, neck, or lips.

Flat Warts: Flat warts, which are more common among children and young adults, usually appear in groups as smooth yellow-brown, pink, or flesh-colored spots, most frequently on the face and tops of the hands. The beard area in men and the legs in women are also common locations for flat warts, where they may be spread by shaving.

Genital Warts: Also called venereal warts or condylomata acuminata, genital warts occur on the penis, anus, vulva, vagina, and cervix. They are irregular, bumpy growths often with the texture of a small cauliflower (see Sexually Transmitted Diseases: Genital Warts).

Did You Know...

  • Warts are most often spread from one part of the body to another, but they can spread also from one person to another.

Diagnosis

Doctors recognize warts by their typical appearance. Growths on the skin that cannot be definitely identified may need to be removed for examination under a microscope (biopsy).

Treatment

Many warts, particularly common warts, disappear on their own within a year or two. Because warts rarely leave a scar when they heal spontaneously, they do not need to be treated unless they cause pain or psychologic distress. Genital warts are more likely to persist and are more contagious, so doctors often remove them or treat them with drugs. All types of warts may recur after removal. Plantar warts are the most difficult to cure.

In general, warts can be removed with the following:

  • Chemicals: Typical chemicals used include salicylic acid, trichloroacetic acid Some Trade Names
    TRI-CHLOR
    , cantharidin, and podophyllin. Flat warts are often treated with peeling agents such as retinoic or salicylic acid. 5- Fluorouracil Some Trade Names
    ADRUCIL
    cream or solution may also be used. Imiquimod Some Trade Names
    ALDARA
    , a new cream for the treatment of genital warts, is sometimes used to treat other warts. Some chemicals can be applied by the person, but others must be applied by a doctor. Most of these chemicals can burn normal skin, so when they are applied at home, directions must be followed carefully. Chemicals usually require multiple applications over several weeks to months. The wart is scraped either at home or in the office to remove dead tissue before each treatment.
  • Freezing (cryotherapy): Freezing is safe. It does not usually require that the area be numbed but may be too painful for children to tolerate. Warts may be frozen with various commercial freezing probes or with liquid nitrogen sprayed on or applied with a cotton swab. Cryotherapy is often used for plantar warts and warts under the fingernails. Multiple treatments at monthly intervals are often required, especially for large warts.
  • Burning and cutting: These methods are effective but are more painful and usually leave a scar. A laser or electrical current is used to burn warts off. A pulsed dye laser is also effective but, like freezing, usually requires multiple treatments (see Noncancerous Skin Growths: Using Lasers to Treat Skin ProblemsSidebar).

Last full review/revision October 2008 by James G.H. Dinulos, MD

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