Why Do Children Pick Their Nose?

In a clever series called 10 Mysteries of You: Ten things we don’t understand about humans in New Scientist, Australian science writer Emma Young includes some obvious ones (blushing, altruism, dreams, art) but ends her list with a surprise: nose-picking. This had not occurred to me:

It is possible that ingesting nasal detritus might help build a healthy immune response – after all, researchers investigating the hygiene hypothesis have built a large body of evidence indicating that lack of exposure to infectious agents can increase one’s susceptibility to allergic diseases.

This seems to be Young’s idea rather than that of the scientist she spoke to. She has her hygiene hypothesis stuff wrong. The original hygiene hypothesis was indeed that lack of exposure to infectious agents can increase allergies — but the data later collected did not support this. More infections in childhood did not correlate with less allergy. What did seem to help was exposure to dirt. Apparently the dirt was helpful whether or not it was infectious (= contained something that could make you sick). The nose-picking data (kids pick their nose a lot and sometimes eat the stuff) does make sense given my umami hypothesis, which says that exposure to bacteria is good for us. You couldn’t get sick from eating what comes out of your nose but as it leaves your nose foreign bacteria grow on it; so eating your snot is a way to introduce foreign bacteria into your digestive system. Which the umami hypothesis says is needed for health.

Do kids who eat more fermented food eat less snot? As I posted earlier, since I started eating lots of fermented food, my desire for fancy restaurant food has gone way down.

Thanks to JR Minkel.