Warts are infectious growths in the outer layers of the skin. Because they are contagious, they can spread from person to person or from one site to another on the same person. Most frequently, warts appear on the hands and fingers and on the soles of the feet. However, they can emerge anywhere on the skin, including the genital and anal areas.

Causes

Common warts are caused by exposure to a virus called the human papilloma virus. The virus can remain inactive for up to six months after contact before causing the eruption of abnormal skin masses.

The virus is transmitted to another person or another site on the body by direct contact. For example, brushing or combing the hair can spread the virus from a wart on the scalp. Shaving or scratching a given area on the body and then touching another area will also transmit the virus. In addition, moist parts of the body, such as the soles of the feet, provide a breeding ground for growth of the virus.

As people become older, they seem to develop an immunity or resistance to the wart virus. For this reason, children tend to acquire warts more frequently than adults. Nevertheless, warts can occur at any age.

Symptoms

Usually, warts appear as firm gray masses that feel tender or itchy. Their size and shape vary depending on the location and severity of the viral infection. Children are most likely to have flat warts, particularly on the face. This variety looks smooth, flat, and yellowish brown.

Plantar warts grow on the soles of the feet, where they can become as large as two inches in diameter. These warts cause considerable pain because the tissue swelling pushes inward. (The discomfort from plantar warts feels like walking with a pebble in your shoe.)

Most warts are not health-threatening. However, when they are extensive in number, they can cause extreme sensitivity or pain.

Treatment

Studies have shown that two out of every three warts disappear on their own, usually within two years. Consequently, physicians usually recommend leaving warts alone unless they are causing discomfort or obstruction.

Doctors sometimes treat one or two warts and find that the patient's other warts also clear up. A possible explanation is that the original treatment stimulates the manufacture of antibodies (protective substances) that fight the virus in other warts.

There are over-the-counter preparations to aid removal of warts. Most of these remedies contain a form of acid, which is dangerous if not used according to directions. Although some of these drugs are effective, only a doctor should remove a wart.

Physicians may try a variety of topical preparations to loosen the warts. A solution containing cantharidin, a substance that causes blistering, may be applied directly to the wart. About one week after application, the doctor should be able to remove the wart with a surgical knife or scissors. Corn plasters containing salicylic acid soften the wart so that it can be scraped away.

When a wart persists, physicians may advise surgery to remove affected tissue. Electrosurgery dissolves wart tissue with electric current. Cryotherapy freezes the area with dry ice or liquid nitrogen; freezing allows the wart to be lifted off easily.