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Common warts (verruca vulgaris) are more of a nuisance than a serious health problem, but they are interesting. There is a whole mythology surrounding their cause (touching toads?) and treatment (everything from banana peels to vitamin C). Many people believe they can be made to vanish by suggestion or hypnosis. I used to believe that too.

Every doctor has wart stories. Here are some of mine.

A patient made an appointment to see me because he had a wart, but when he tried to show me his wart he discovered that it had vanished! Apparently, just making the appointment cured it.

Another patient did have obvious warts and I prescribed the “wart medicine” that our pharmacy tech compounded, based on salicylic acid. He was out of one of the ingredients and had to ask my patient to return in a week. When she returned, her warts were already gone. The wart medicine apparently worked so well that you didn’t even have to use it!

I worked with a dermatologist who used a colorful laminated card with a picture of a toad to stroke children’s warts, telling them it was a wart remover. In his experience, this would frequently make the wart vanish over the next few days. Was this ethical? Was he lying and deliberately deceiving patients, or could this be excused as playing make-believe to distract the child and improve his attitude about the wart?

He was certainly deceiving himself in thinking that this foolishness was actually effective based on his own uncontrolled observations. Hypnotists claim success in treating warts with direct suggestion: they say that prepubertal children respond almost without exception, although it is less effective in adults. I was taught that if a patient had multiple warts and you treated just one of them, the others would likely vanish too. This might sort of make sense if the treatment stimulated an immune response, but I haven’t seen any evidence to support it.

What can science tell us about warts?

A new review article in American Family Physician, “Treatment of Nongenital Cutaneous Warts” by Mulhem and Pinelis provides a thorough update of the current evidence.

Cutaneous warts are epidermal proliferations caused by over 100 types of human papillomavirus. They are spread person-to-person or by contact with contaminated objects. They are most common in children. Walking barefoot is a risk factor for plantar warts (warts on the sole of the foot that that have a different appearance due to being under pressure). Nail-biting, meat handling, and immunosuppression are also risk factors. 90% of renal transplant patients develop warts.

Warts are usually self-limited. Half resolve spontaneously in a year, two-thirds within two years. Watchful waiting is an option, but patients often want treatment because of discomfort or social stigma. Two treatments have been clearly proven effective by scientific studies: salicylic acid and freezing with liquid nitrogen. There is limited evidence for silver nitrate, topical fluorouracil, and topical zinc. There is little to no good evidence for cantharidin, dinitrochlorobenzene, oral cimetidine, oral zinc sulfate, podophyllin, propolis ointment, retinoids and topical garlic extract. A few years ago, duct tape was reported to work, but subsequent studies showed that it probably does not. Warts can also be surgically removed, and dermatologists can offer specialized treatments such as intralesional bleomycin and pulse dye laser.

I found it interesting that the AFP review didn’t even bother to mention hypnosis, suggestion, or CAM .

Salicylic acid preparations are available over the counter for self-treatment. They are well tolerated and produce a 73% cure rate in 6 to 12 weeks. Cryotherapy with liquid nitrogen is equally effective but is more expensive, requires multiple office visits, and can cause pain, blistering, pigment changes, and other complications (tendon or nerve damage, scarring), especially if used too aggressively. A combination of cryotherapy and salicylic acid may give the best results. If a treatment caused permanent scarring, that would be worse than the disease.

To take a page from Mark Crislip’s job description, the patient has the mindset “Me have wart. You cure wart. Me go home.” The health care provider can re-frame the issue as “You have wart. Me educate. You think. We discuss.” Since warts are benign and self-limited, the option of not treating should always be on the table.

What about CAM ?

Warts provide a fertile field for CAM . Various CAM modalities (chiropractic, acupuncture, homeopathy, energy medicine, etc.) have been claimed to cure warts. Acupuncturists have claimed a 90% success rate in only 1-3 weeks. PubMed lists a recent article about treatment with “sparrow-pecking” moxibustion that sounds intriguing, but no abstract is available. When warts follow their natural history and resolve, CAM is happy to take the credit. When they fail to resolve, CAM can continue treatments and continue to generate income. It’s a cash cow and ideal CAM fodder. Since warts are so common, potential clients are plentiful.

I used to believe that warts could be wished away. Now that I am older and wiser, I think warts vanish because of the natural course of the disease, not because of suggestion. Observers have reached false conclusions due to the post hoc ergo propter hoc (correlation is not causation) fallacy. Warts that went away after suggestion didn’t go away because of suggestion. The many folk remedies, like banana peels, were perpetuated by similar errors in reasoning. No matter how much we wish mind-over-matter worked, warts can’t be wished away: that’s the truth, warts and all.