The Medical Minute: The worry with warts

August 04, 2010

By David Adams and Michael Lynch

Common warts are harmless skin lesions that are usually found on the hands or soles of the feet, the latter referred to as plantar warts. Warts have a fleshy and hard feel to them, can be associated with skin thickening, and often are described as having a cauliflower-like appearance. Warts, especially plantar warts and those developing near fingernails are sometimes painful. Plantar warts are also slow to spontaneously heal and can be more difficult to treat.

Collectively, these non-genital warts are harmless lesions that for most people heal completely, without treatment in several months to years. Unless warts cause pain, there are no immediate reasons for treatment. Many people find warts to be aesthetically unpleasing and warts carry a degree of social stigma that drives many to seek medical treatment.

What causes warts?

Warts are caused by members of a virus family known as papillomaviruses. Human papillomavirus (HPV), of which there are more than one hundred types, infects the cells that comprise the outer layer of skin. The virus enters the skin cells and incorporates itself into the DNA. There, the virus multiplies, induces abnormal growth of the skin, and is released by the natural shedding of skin to potentially infect others. HPV types 1, 2, and 4 cause most common warts, but other HPV types have been implicated. These viruses are in the same family of viruses that causes genital warts (an entirely separate topic), but it is important to emphasize that common warts are not sexually transmitted.

How do you get warts?

HPV can be spread by direct contact with the warty skin of an infected person, although most contacts do not result in transmission. That is, warts are contagious, but not highly contagious. The virus also may be spread via contact with contaminated towels or surfaces such as gymnasium equipment, locker room floors, or swimming pool decks. Proper hand and foot hygiene is recommended to reduce infections.

Self-inoculation may explain multiple warts on the same person and people with damaged skin or who are immunosuppressed are at increased risk for HPV infection. When warts are treated immediately, this reduces risk of transmission to self or others.

What are the treatment options for warts?

If you are not immunosuppressed, and the warts are not painful, bothersome, or increasing in number, a cautious watch and wait approach can be used, but with some increased chance of transmission to others. Your body will often fight off the viral infection in time, and the warts will heal without treatment in many cases. This however may take months to years and generally occurs much faster and more consistently in children.

For those who desire medical therapy, there are several options available both over the counter and from your doctor.

Over the Counter Options

The most popular and effective therapy is a combination of salicylic acid 17 percent liquid preparation covered by a plaster which contains 40 percent salicylic acid in a cotton material. This can all be taped in place with medical tape, a bandaid, or vinyl waterproof tape. The tape is removed every 1-3 days, and the “dead” skin is removed and followed by reapplication of the above preparation. Applying this method for several weeks or months provides a cure in most cases.

Over the counter “freeze” products containing dimethyl ether and propane take the skin down to negative 57 degrees Celsius but generally are not cold enough to treat most warts.

Physician Options

If the wart is not responding to over the counter therapies or you are not sure if it is a wart, consulting your primary care physician or dermatologist is recommended. A variety of medications and procedures can be offered to you.

  • Cryotherapy involves freezing the wart with liquid nitrogen (negative 196 degrees Celsius). This procedure may require several treatments before the wart resolves.
  • An In office application of trichloroacetic acid and other agents.
  • Immunotherapy may include imiquimod 5 percent cream which improves host immune response to the virus or 5-fluorouracil 5 percent cream which inhibits viral proliferation.
  • Bleomycin injections, with repeat injection in 4 weeks if needed. The drug causes local death of infected cells.
  • Laser treatment is expensive but sometimes useful.

For additional information about common warts, visit

David Adams, M.D., assistant professor of dermatology, Penn State Milton S. Hershey Medical Center and Michael Lynch, B.S., medical student at Penn State College of Medicine.

(Media Contacts)

Last Updated August 10, 2010