If you're afraid of toads because you've heard that touching them causes skin warts, you can relax around the little creatures. Warts are simply an overgrowth of skin cells caused by infection with the human papilloma virus. Toads have nothing to do with their spread--humans do.
The virus is spread either through direct skin-to-skin contact, or indirectly, through contact with a surface that has been contaminated with the virus that has been shed from a wart.
But you don't have to fear human contact either, because even if you come into contact with the virus that causes warts, the risk of becoming infected is small.
We're not sure why some people develop warts and others don't after exposure to the virus, or HPV. You don't develop a wart every time you shake hands with a person who has one, just as you don't become sick every time you come into contact with someone with a cold. And although people of all ages can get warts, infection is significantly more common among children and young adults (immunity to the virus may develop with age).
Several things can increase the likelihood of infection. Individuals with poorly functioning immune systems, such as people with AIDS or those taking immunosuppressants, are at higher risk of infection than those with healthy immunity. Infection is also more likely to occur to damaged skin. Habitual nail-biters, for example, tend to develop warts on their fingers more frequently than non-biters.
Even seemingly mild trauma to the skin, such as walking on a rough surface like a pool deck, appears to disrupt the integrity of the skin sufficiently to increase the risk of infection. For this reason, public pools are commonly blamed for the spread of warts on the feet. A simple way to prevent this is by wearing water sandals or other protective footwear around pools and in communal bathing areas like locker rooms.
Warts may be diagnosed as "common" or "plantar" warts, according to their location (although they are all caused by the same virus). Common warts usually involve the hands. They are typically skin-colored lesions that protrude from the skin's surface and are rough to the touch; they're frequently described as having a "cauliflower-like" appearance.
Plantar warts involve the bottoms of the feet and are sometimes confused with calluses. Unlike common warts, they do not stick up above the surface of the skin because the pressure of walking flattens them, pushing them back into the skin. Although unsightly, common warts generally present no real discomfort or problem; plantar warts, on the other hand, may be uncomfortable, even painful.
(Genital warts are also caused by the human papilloma virus but typically involve different strains. They are spread by sexual contact and are treated differently than common or plantar warts.)
Because of their characteristic appearance, most warts can be diagnosed easily. Treatment, however, is not nearly as straightforward. In many cases, doing nothing at all--"watchful waiting," as it is sometimes called--is a perfectly acceptable option. Given sufficient time, many warts will resolve on their own, especially in children and adolescents. Nearly one-third of all warts in children will resolve spontaneously within three months; about two-thirds will disappear within two years (perhaps because the body develops immunity to the virus). Although there is a small risk of spreading the infection to another part of the body or to someone else, there is no other downside to waiting. Warts that don't disappear on their own can be treated later.
More immediate treatment is necessary when warts--for example, on the hands--present a cosmetic problem or interfere with daily activities. Plantar warts may need attention if they are very uncomfortable or painful.
When treatment is indicated, most physicians agree that it is best to start with simple therapies. Although no treatment is 100% effective, over-the-counter products do fairly well, producing cure rates as high as 70% to 80%. These products contain chemicals such as salicylic acid, which works by destroying the virus-infected skin cells. These types of products are not generally recommended for warts on the face because of the potential for scarring.
It's important to use these preparations exactly as directed. Daily application is usually required and may need to be continued for up to three months. To promote penetration of the product into the wart, the skin should first be rubbed lightly with an emery board or pumice stone and immersed in warm water. To protect healthy skin surrounding the wart, petroleum jelly or another type of protective coating should be applied.
For warts that fail to respond to these self-treatment measures, more aggressive therapies are available. For example, stronger prescription medications can be applied to the wart by a physician, or the infected cells can be killed by freezing them with a procedure called cryotherapy (although a recent British study has questioned the effectiveness of this method). When all else fails, warts can be excised, or cut out.
Dr. Jonathan Fielding is the director of public health and the health officer for the Los Angeles County Department of Health Services. Dr. Valerie Ulene is a board-certified specialist in preventive medicine practicing in Los Angeles. Their column appears the second and fourth Mondays of the month. Send questions to firstname.lastname@example.org. They cannot respond to every query.