The following article was published on The Conversation.

Monday’s medical myth: warts aren’t contagious

By Michael Tam, University of New South Wales

As a general practitioner (GP), I see a lot of warts. They’re a common skin complaint that most people experience at least one in their lives. Common warts are small dome-shaped lumps on the surface of the skin, typically on the back of fingers, hands, toes, and the front of the knee.

Patients who come in with common warts have usually guessed the growths on their skin are “warts”. But I’m often asked whether they’re contagious and whether any of the old wives’ tales work as cures.

The classic myth that warts are caused by touching toads is, of course, untrue. There are many folk remedies for warts that range from the magical (blacksmith’s water – the water that hot iron has been plunged), to the bizarre (taking a dead cat to a graveyard at midnight), and the gruesome (dripping the blood from the head of a decapitated eel onto the skin).

About a third of common warts will disappear in three months, and most in two years. So this might explain why these treatments were considered effective.

We now know that warts are due to infections from a specific group of viruses – human papilloma viruses (HPV), of which there are over a hundred known subtypes.

HPV came into the spotlight when Gardasil, the “cervical cancer” vaccine, became part of the Australian immunisation schedulefor girls and young women. From 2013, the HPV vaccination program will include 12- and 13-year-old boys.

Although some types of HPV can cause cancers (genital, oral, throat), the types of HPV that commonly cause warts on the face, hands and feet do not. And the types of HPV that cause genital warts are different to the ones that cause common warts.

Gardasil, for instance, protects against HPV types 6, 11, 16 and 18. Types 6 and 11 cause about 90% of genital warts, and types 16 and 18 cause about 70% of cervical cancer.
Since the HPV immunisation started in Australian, there has been a big drop in the rate of genital warts.

Warts are contagious: HPV can be transmitted by direct contact through minor injuries in the skin. After infection, there can be a latency of weeks to years, so warts can appear to come out of the blue.

But rest assured, if you have a common wart on your fingers, you are not going to give yourself genital warts, or even plantar warts, if you touch those parts of your body. Different types of warts are typically caused by different types of HPV, so you could potentially infect the other hand.

So how do you treat common warts?

It’s important to remember that most will go away with no treatment within about two years. The topical over-the-counter treatments (such as salicylic acid and podophyllotoxin) do work, but require patience and persistence. Cryotherapy with liquid nitrogen, performed by your GP, is probably more effective if you want to get rid of your warts quickly. Nothing works that well for plantar warts.

A wondrous variety of wart treatments live on in the modern day. Banana peel ranks high on a Google search but lacks research evidence (and there is little reason why it should work). The popular practice of using duct tape doesn’t seem to be effective.

We may have moved on from touching toads but wart myths are alive and well.

Michael Tam is a community general practitioner and consults with patients who have warts. He otherwise does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published at The Conversation.
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