Nose picking is an entirely natural habit — children who have not yet learned social norms realise very early on that the fit between their forefinger and a nostril is pretty good. We all pick our noses and often examine the product. Other primates do it too. Compulsive nose picking is known as rhinotillexomania.
Some people eat the mucoid plaques (the technical term is mucophagy, meaning “mucus feeding”) but less commonly in public because the social stigma around nose picking is widespread. Apart from being considered disgusting, it means ingesting inhaled mucous-bound germs, toxic metals and environmental contaminants. There’s also the risk of gouging and abrasions inside the nostrils, which can allow pathogenic bacteria to invade the body.
Nasal mucous and its antibodies and enzymes are the body’s front line immune defence system against infections. Cells in the nasal passage called goblet cells (named after their cup-like appearance) generate mucous to trap air-borne viruses, bacteria and dust containing potentially harmful substances like lead, asbestos and pollen. The dust, microbes and allergens so captured eventually get ingested as that mucus drips down the throat.