DEAR MAYO CLINIC:

If I don't treat the wart on my hand, is it true that it could cause other warts or spread to other people?

ANSWER:

Yes, warts can spread if left untreated, and the virus that causes warts can be passed to another person. By adulthood, though, most people have developed immunity to the viruses that cause warts. Therefore, it's unlikely that an adult would develop warts as a result of contact with a person who has a wart. Children are more susceptible, however, because their bodies are less likely to have built up immunity to the virus.

Warts are caused by human papillomavirus (HPV). This virus is very common, and people are exposed to it almost continuously. The virus has more than 100 types -- the reason there are so many different types of warts. Some strains of HPV are acquired through sexual contact. Most forms, however, are spread by casual contact or indirectly through shared objects, such as towels or washcloths.

Over time, people develop immunity to most types of HPV that cause common warts; their bodies are no longer affected by the virus, and it can't take hold and grow. But it takes a long time for that to happen. As a result, warts are widespread in children and young adults because their bodies haven't yet had enough time to become immune to this common virus.

When HPV does take hold, it grows a lump of thickened skin. That's the wart. The skin on a wart will shed over time, just as normal skin sheds. That skin, when shed, carries the virus with it. If someone touches the shed skin -- whether directly through skin-to-skin contact or indirectly, for example, through a towel, the floor of a swimming pool or a carpet, then the virus could spread. But infection occurs only if, first, the skin can be penetrated through a crack, scrape or some other opening, and, second, the person has not developed immunity to HPV.

Once a wart begins to grow, HPV stimulates the skin to attract and grow its own blood supply and nerves, which makes the wart very hearty and less likely to go away on its own. If left untreated, most warts will persist for one to two years. Eventually, though, the body will recognize the virus and fight it off, causing the wart to disappear. While they remain, however, warts can spread very easily when people pick at them or when they are on the hands, feet or face.

Small warts that are not bothersome don't require treatment. They're harmless and will eventually go away. If you don't want to wait or if a wart is causing discomfort, over-the-counter remedies, such as salicylic acid, are available to treat warts.

For larger, painful warts or for those that don't respond to over-the-counter treatment, a dermatologist can offer additional options. Commonly, these include prescription antiviral creams, prescription therapies that irritate and eliminate warts, and medications that stimulate the immune system or disrupt the wart's skin cell growth. Rarely, stubborn warts require minor surgery to cut away the tissue or laser surgery to remove the wart.

If you are an adult who never had problems with warts but they suddenly begin to develop, see your doctor and ask to be screened for an immune system disorder. Adults usually don't have new-onset, common warts. But if numerous warts begin to appear, the immune system may be malfunctioning. In that case, a prompt evaluation is recommended.

Dawn Davis, M.D., Dermatology, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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