Poking around inside our nostrils is disgusting, unhygienic and potentially harmful, so it’s baffling that it’s as common as it is, says Jason G Goldman.

Most of us do it, but few of us will admit to it. If we get caught red-handed, we experience shame and regret. And we tend to frown upon others when they do it in public. I'm talking, of course, about reaching up into your nostrils with a finger in an effort to scrape out snot. Is nose-picking really all that bad? How prevalent or bad is it, really? And why (really, why?) would anybody ever decide to see what snot tastes like?

The formal medical term used to describe the act of picking one's nose is “rhinotillexomania”. The first systematic scientific study of the phenomenon may have been undertaken as recently as 1995, by a pair of US researchers named Thompson and Jefferson. They sent a survey by mail to 1,000 adult residents of Dane County, Wisconsin. Of the 254 that responded, a whopping 91% of their respondents confessed to picking their noses, while only 1.2% could admit to doing it at least once each hour. Two subjects indicated that their nasal mining habits interfered with their daily lives (moderately to markedly). And, to their surprise, two other people reported so much nose picking that they had actually picked a hole right trough their nasal septum, the thin tissue that separates the left and right nostrils.

It wasn't a perfect study; only about a quarter of those surveyed responded, and those who already had a personal interest in nose picking may have been more likely to complete and return the survey. Still, it underscored the likelihood that nose picking, despite its cultural taboos, is pretty widespread.

Young habit

Five years later, doctors Chittaranjan Andrade and BS Srihari of the National Institute of Mental Health and Neurosciences in Bangalore, India, decided to look a little deeper into nose-picking. They reasoned that most habitual behaviours are more common among kids and teenagers than among adults, so it made sense to survey younger populations rather than older populations, to get a sense for how prevalent nose picking might be. In addition, knowing that the Wisconsin study suffered from a possible response bias, they distributed their surveys in school classrooms, where they would have a much higher likelihood of getting a representative sample. They focused on four schools within Bangalore, one catering to children from families of lower socioeconomic status (SES), two whose students tended to come from middle-class families, and a fourth school where students came from higher-earning households.

In all, Andrade and Srihari compiled data from 200 teenagers. Nearly all of them admitted to picking their noses, on average four times per day. That's not all that enlightening; we knew this. But what are interesting are the patterns. Only 7.6% of students reported sticking their fingers into their noses more than 20 times each day, but nearly 20% thought they had a “serious nose-picking problem”. Most of them said they did it to relieve an itch or to clear out nasal debris, but 24 of them, i.e. 12%, admitted that they picked their nose because it felt good.

And it wasn't just fingers. A total of 13 students said they used tweezers to pick their noses, and nine said they used pencils. Nine of them – nine! – admitted to eating the treasures obtained from their nose picking activities. Yum.

There were no differences according to socioeconomic class; nose picking is something that truly unites us all. There were, however, some gender differences. Boys were more likely to do it, while girls were more likely to think it a bad habit. Boys were also statistically more likely to have additional bad habits, like biting their nails (onychophagia) or pulling out their hair (trichotillomania).

Facial mutilation

Nose picking isn’t just a harmless activity, though. In some extreme cases, nose-picking can cause, or be related to, more serious problems, as Andrade and Srihari found when they reviewed the medical literature. In one case, surgeons could not achieve complete, lasting closure of a perforated nasal septum because a patient couldn’t stop nose picking, preventing the surgical site from healing. Then there was a 53-year-old woman whose chronic nose picking not only led to a perforation of her nasal septum; she actually carved a hole into her sinus.

And there was a 29-year-old man who had a previously undocumented convergence of trichotillomania (hair-plucking) and rhinotillexomania (nose-picking). It forced his doctors to coin a new term: rhinotrichotillomania. His behaviour involved compulsively pulling out his nose hairs. When his hair pulling got too extreme, his nose would become inflamed. To treat the inflammation, he began applying a solution that had the side effect of staining his nose purple. To his surprise, the purple stain concealed his visible nose hairs, making him far more relaxed. He was actually more comfortable leaving the house with a purple nose than with visible nose hairs. His doctors, who succeeded in treating him with drugs, describe his compulsion as a manifestation of body dysmorphic disorder, which is sometimes thought of as an "obsessive compulsive spectrum disorder".

Nose for danger

Most of us can rest safe knowing that our occasional, discreet nose picking is probably not the pathological variety. It's interesting that despite the fact that nail-biting and nose-hair plucking are well-recognised manifestations of obsessive-compulsive disorder, rhinotillexomania is generally not.

But that doesn't mean it's completely safe. In a 2006 study, a group of Dutch researchers found that nose picking can help bacterial infections get around. They discovered that nose pickers at an ear, nose, and throat clinic were more likely to carry Staphylococcus aureus bacteria in their noses than non-pickers. Among healthy volunteers, they found something similar: a positive correlation between self-reported nose-picking frequency and both the frequency with which their nasal cultures housed the nasty beasties, and the amount of S. aureus present in those cultures.

So, given all these risks, and the potential for provoking disgust in other people, why do we still do it? There are no clear answers, but as Tom Stafford wrote recently about nail-biting, perhaps it’s a combination of the simple satisfaction we derive from ‘tidying-up’ and the fact that our nose is within easy reach all the time – in other words, we pick it ‘because it’s there’.

Or perhaps nose picking is just evidence of laziness. Fingers, after all, are never in short supply when you feel the urge to clear your nostrils. Which is more than can be said about a box of tissues.

It's gratifying to know that some researchers are still trying to understand the reasons we pick our noses and the consequences that arise from it. In 2001, the Indian researchers, Andrade and Srihari, were recognised for their work with an Ig Nobel prize, which is given for research that first makes you laugh and then makes you think. At the ceremony, Andrade remarked, "some people poke their nose into other people's business. I made it my business to poke my business into other people's noses."

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