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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Medical Myths Medical Myths

Toads and Frogs -- Friend or Foe?

October 10, 2013

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center

The idea that contact with toads or frogs may cause warts is probably ancient — it certainly goes back at least as far as my childhood — and it may relate to the fact that their surfaces are bumpy and resemble warts. But it is truly a myth, one that has survived despite assurances to the contrary. In fact, these amazing creatures have abilities much more impressive than causing warts — some can change their sex, and one species, now thought extinct, reportedly deliver their babies from their mouths! But, I digress ...

The Real Cause of Warts

Warts are caused by human papillomavirus (HPV). This virus can be transmitted through contact, but not through contact with amphibians. Rather, it is transmitted through human contact. Walking with bare feet in a public place (for example, the showers at a gym or health club) is one way to pick up this virus from another person.

Warts often require no treatment and resolve on their own in a year or two. However, treatment for warts in the genital area of men or women is recommended because when associated with genital warts, HPV increases the risk of cervical cancer. For warts in other locations, treatment is suggested only if the warts are painful, are cosmetically unacceptable or are bothersome in some other way.

It's important to know about a newly approved vaccine that's available to help prevent HPV infection.

More Amphibian Myths

Now back to frogs and toads. The lumpy, slimy coating that covers these harmless animals makes them unpalatable to many predators, and perhaps the myth about warts has successfully protected them from humans as well. Other medical myths surrounding frogs and toads include the following:

  • The ability to cause or cure hallucinations — In many cultures, frogs are thought to have the power to alter one's mental state, a belief that has some merit because a few frog species contain compounds that are toxic to the nervous systems of humans and reportedly cause hallucinations when ingested.
  • The ability to detect poison — Classical Greek and Roman writers — and more recently Shakespeare — have described a "toad stone" located inside a toad's head. They purport that the toad stone, if worn in a necklace or a ring, would become warm or change color if near a poisonous substance, thereby alerting the wearer.
  • The ability to improve fertility — Women in ancient Egypt believed that frogs embodied rebirth and renewal (perhaps because of their dramatic metamorphosis from tadpoles). They often wore charms in the shape of frogs to increase reproductive success.

The Bottom Line

Just as the story of the frog prince is mythical, so is the story of frogs or toads causing warts. So although kissing frogs (or toads) is not recommended, you need not worry if you happen to touch one.

For more information about frogs, visit the following Web site:

Robert H. Shmerling, M.D., is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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