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What are warts?  Warts are benign skin growths caused by the human papilloma virus (HPV). The virus, which is acquired through cracks in the skin, causes a thickening of the outer layer of skin. Warts affect 7-10% of the population, and young people are more commonly affected. Most warts are not worrisome, medically speaking, and are primarily of cosmetic concern except when causing discomfort, particularly on the bottom of the feet.

Transmission: Warts are transmitted by direct contact or indirect contact (e.g., public showers or swimming pool areas). They can be transmitted to one's self or others. Picking or scratching at warts can increase the risk of transmission. Trauma may play a role in the development of warts as they often occur at pressure points, for example, on the bottom of the foot.

Types of warts:  Each type of wart is caused by a slightly different virus and treatment may vary. The common forms include the following:

Common warts (verruca vulgaris) are flesh-colored, small raised spots on the skin with a rough surface. The size of the wart varies and may appear anywhere on the skin, particularly on the elbows, knees, hands, fingers and around the nails. The black dots found in these warts, often called seeds, are superficial blood vessels and not actual seeds. 

Plantar warts (verruca plataris) are no different than common warts except that their location on the bottom of the foot may result in a flat appearance from being pressed into the foot by the weight of the person. Plantar warts may occur singly or in a pattern, grouped closely together. They may cause pain, redness and swelling. See Images on Wikipedia.

Flat warts(verruca plana) have a smaller, smoother surface than common warts. They may appear in great numbers on the face and may also occur elsewhere, particularly on the arms and legs. 

Genital warts (condylomata accuminata) may be small or large. When large, they may have a cauliflower-like appearance. They grow on warm, moist surfaces such as the genital and rectal areas. They are usually, but not always, sexually transmitted. Do not treat genital warts yourself; medical treatment is necessary. These warts are commonly treated with weekly applications of podophyllin, liquid nitrogen or other agents, which may be irritating to the skin. Genital warts are common, contagious and may be difficult to eradicate. See also:

Self-care:  You can treat warts, except genital warts, without visiting a doctor. Apply salicylic acid liquid or plasters (available without prescription) according to package directions. If using liquid, cover the wart with a waterproof adhesive tape like duct tape or white athletic tape. After 2-3 days, soak the area in warm water, then scrape away the dead gray/white skin with a pumice stone or metal nail file. Repeat until the wart has disappeared.

Duct tape alone as an occlusive dressing has been effective at resolving warts. See article on "Duct Tape More Effective than Cryotherapy for Warts" in the American Family Physician Journal.

If the wart does not completely disappear, see a clinician for medical treatment.

Medical treatment: Warts often disappear spontaneously over several years. If warts are painful, subject to infection or cosmetically objectionable, they should be treated. Treatment depends on the size, location and number of warts as well as the activities of the infected person. Warts may be very difficult to cure; often multiple treatments are needed, and even then treatment success cannot be guaranteed. Types of treatment include the following:

Cryotherapy (liquid nitrogen) is used on many warts at UHS. First, any dead skin surrounding the wart may be scraped off. Next, liquid nitrogen is applied, producing an uncomfortable blister within two days of treatment. Many warts require more than one treatment with the second treatment being performed 2-4 weeks after the first.

Electrodessication (electrocautery) is usually used only after warts have not responded to other procedures. It consists of burning the wart with a high frequency current, followed by scraping the surface. It should be used cautiously as it may occasionally cause scarring. This process is rarely used at UHS.

Salicylic acid is often used for plantar warts. A 40% salicylic acid plaster is cut to the size and shape of the wart and covered with an occlusive tape (e.g., duct tape). Alternatively, a 17-20% liquid may be applied. After 24 hours, the wart is pared down. This is repeated every day if the area is not too irritated. This method may be used at UHS. Salicylic acid is also available without prescription; follow package directions and do not use on genital areas.


Remove warts that are present.

Do not pick at warts to avoid spreading them.

Wear footwear in public showers and other public areas to avoid plantar warts.

Use condoms for intercourse. Condoms reduce but do not eliminate the risk of HPV transmission.

For more information:


  • Schedule an Appointment: Appointments are required for most medical services, however options are available for urgent concerns.

  • Nurse Advice by Phone is available day and night, which may save a trip to UHS, the ER or an urgent care facility.