For what seems like time immemorial, we've been telling our kids to stop putting their fingers in their nose. And, for the love of dogs, to please, please stop eating what they find in there.
Now, recent research shows that picking your nose – and eating the mucus within – can actually be good for you.
The study, published in the journal Applied and Environmental Microbiology, showed that eating your nasal mucus (a.k.a 'snot') can be good for your teeth.
That's because snot contains salivary mucins, the components that form a barrier against the bacteria that can cause cavities.
Forming that barrier can stop bacteria from latching onto teeth and secreting acid that can penetrate your tooth's enamel and cause nasty holes.
Scott Napper thinks picking your nose – and eating what you find – may be good for your immune system, too.
The biochemistry professor at the University of Saskatchewan is a father of two, who became interested in the topic after watching his two daughters pick their nose and eat their snot.
"From an evolutionary perspective, we evolved under very dirty conditions and maybe this desire to keep our environment and our behaviours sterile isn't actually working to our advantage," he said in a 2013 interview with CBC news.
This certainly fits in with the hygiene hypothesis, which states that children who grow up 'too clean' (as in, in overly sterile environments with limited exposure to infections) may have an increased risk of conditions such as asthma and allergies.
And picking your snot and eating it is certainly one way to avoid being 'too clean'.
Another reason nose-picking may be good for you was highlighted in research published in 1995, which showed that mucins may also help defend yourself against respiratory infections.
In spite of the studies piling up in favour of the habit, we still have to wonder: isn't it bad for you?
Not necessarily, says GP Dr Michael Fasher, Adjunct Associate Professor at the University of Sydney.
"Nose picking is not a health risk to the picker himself, nor is it a risk to the health of others - [if they have] good hand washing habits."
Picking your nose can cause bleeding, warns Dr Fasher. However, he says it's actually an uncommon cause of nose bleeding.
Mind you, he says, some children appear to pick their nose when they're actually dealing with an underlying issue.
For instance, children with allergic rhinitis have allergies that cause their noses to be itchy and runny. (So they may look like they're picking their nose when they're actually scratching it.)
Other children pick at their noses because they've developed scabs, which they then try to pull off. This can lead to a vicious cycle as picking can lead to scabs, and picking of scabs can lead to infections.
Even if nose picking may have some advantages, parents often prefer to discourage this habit.
If you're trying to stop your child from doing it, Dr Fasher says the trick is to avoid anger or punishment.
"A simple message needs to be delivered as often as necessary but with a tone of voice that is both warm and firm.
"'Johnny, that looks really yucky,' can then be reduced to, 'that's yucky' or even simply one word, 'yucky'."
But if your child's nose picking isn't driving you bananas, Dr Fasher reassures there's no great reason to stop him from doing it – apart from the fact that it's not exactly a good look.