eat boogers practice automucophagy?
The science on this is surprisingly lacking. Maybe you’re one of the normal people that find it gross and refuses to engage in the behavior for fear of breaking social norms.
But what about us, bold thinkers, outspoken intelligentsia willing to thrust through every taboo and cut through any social norms in order to let epistemic rationality and science guide us to enlightenment? Should we eat our own snot?
First, we should look at the question of
picking our nose engaging in rhinotillexis.
There’s a reasonable chance that nose picking is associated with a higher incidence of various types of injury and staph load in the nose. The study has some limitations, the greatest being that it’s very hard to control for the direction of causality (wounds ⇒ nose picking, nose picking ⇒ wounds, wounds ⇒ staph, nose picking ⇒ staph and it’s probably a fairly odd probabilistic causal graph). But it does seem like the frequency of nose picking as a combination of self-assessment and assessment of wounds is a reliable predictor of staph (RR 1.51, p < 0.019). There’s also some evidence that the prevalence of staph in the nose at “subclinical” levels might lead to worse health outcomes. This does suffer from some selection bias, and picking one’s nose might lead to different outcomes between healthy individuals and those visiting an ENT.
It’s also interesting that the trend of % of carriers doesn’t seem to correlate linearly in relation to nose picking, though mean load does.
On the other hand, most children seem to pick their noses at a young age (6-12). The study found a 78% prevalence, but looking at it’s date and terminology used to define demographics its certainly the product of a less rigorous age in medical research. I’ve found another (Ig Noble prize-winning) study being cited as finding “97.5% prevalence in adolescents” but it’s tyrannical guarded by a predatory institution and unavailable on sci-hub, so I can’t validate this claim.
All other studies I could find are case reports of various severe forms of damage caused by nose picking (too many to cite) and studies which would be better classified as opinion pieces (e.g. this one) speculating on various implications based on the previously mentioned staph study and adolescent-focused epidemiology of nose-picking.
So nose picking in itself might be harmful. How harmful? Well, horrendously harmful if you insist too much, maybe-kinda-harmful for an average person in a worst-case scenario, and not at all in a best-case scenario.
Being a good bayesian, this should bias us towards not eating boogers, after all, unless there’s a clear upside, we have indications that the nose picking part is harmful; We could always blow our nose normally and eat the remains, but that’s too gross for even myself to contemplate, for some reason, and I doubt any such interventions have been studies, they await a yet more enlightened age.
Still, the Hobbsians among you are probably celebrating another win for civilization, while fans of Rousseau are likely looking at the frequency of the behavior in children and clamoring that we’re too easily dismissing a natural behavior, obviously helpful in the EAE, tearing town Chesterton’s fence on a mere biased epidemiological whim.
So fine, is there any benefit to picking one’s nose if we proceeded to devour our capture?
My steel-man of the practice is based on this paper's finding of IgA response in the gut based on its microbiota. Bio 101 also tells me I should expect some sort of IgE response due to various antigens collected in the gut.
So if we are to speculate we can think of 4 mechanisms that interplay here:
Dry nasal mucus contains pathogens that have been in part destroyed, damaged or otherwise disabled via mucus binding to them [Likely]
These pathogens provide ample opportunity to develop an immune response in the gut. [Unlikely, oral vaccines work with relatively giant dosages, are less efficacious than IM administered ones, and only work for a very limited set of diseases)
Adaptive immune response to pathogens in nasal mucus which are sampled in the gut might be faster than if they were sampled in the nasal cavity or airways [Very unlikely]
Dry nasal mucus contains samples of pathogens one might later ingest in much larger quantities, such as spores from fungi you could later eat, or bacteria from the ground you’ll later forage food from. [ergh, I guess it could be a thing]
The most plausible story we could craft here is one where eating dry nasal mucus might provide some headway for adaptive immunity against pathogens we might later ingest in larger quantities and better-preserved states. This is very far-fetched but fine, what does the literature have to say?
Maria Jesus Portalatin wrote a whole book chapter about eating mucus, but her analysis seems to take a social and psychological angle, giving us no scientific evidence but some speculation as to its purpose.
There are two interesting roles I’ve not speculated on myself:
It’s a way to “sample” the environment, to “taste the air” so to speak. Whether this has any “use”, especially in our modern environment, is debatable. But we often engage in little useless pleasures, such as insulating the aroma of flowers, sucking on licorice candy, appreciating a prolonged kiss, feeling the texture of velvet, or experiencing the synesthesia bought upon by psychedelics. So there’s certainly a spot for boogers as one of the guilty yet unique culinary pleasures of man, a unique way to taste one’s environment.
It brings about the much more practical possibility that the dry mucus might come into contact with the tonsils (did you know there are 4 kinds of them?), which are heavily implicated in the adaptive immune response, but incapable of producing the amount of mucus or hosting the amount of non-specific immunity that our nasal cavity can. This is a much more plausible explanation for why eating boogers might supplement adaptive immunity to pathogens commonly suspended in the air.
But still, this is empty speculation with not even epidemiological evidence.
I’ve found speculation about mucophagy playing an immunological role in certain species of fish, but they eat the parent’s mucus, from their scales rather than the nose… which they don’t have, being fish and all. So that hardly constitutes any evidence either way and is more alike to the acquisition of antibodies and antigen samples from colostrum.
Why do I bring this up? Because I’ve hit rock bottom, I can find no studies giving mucophagy a fair trial!? There’s some evidence that it’s inherited, under the umbrella of other inherited OCD behaviors.
I’ve found some claims of some inconclusive studies about eating boogers and tooth cavities as well as adaptive immunity. But the supposed author, Scott Napper, doesn’t list them in his biography.
So I’ve followed up with an email, but got no reply, so I am now at an end, lest a better scholar may find something through the archive, or I be bored enough to actually design an experiment on the subject.
Speaking of which…
1 - Enhanced Immune Response
If I were to run an n=1 or self-report study with multiple participants on the subject, I think the design ought to be something like this:
Have two arms, either on the same subject 3-4 months apart, or split between people.
Both arms infect themselves with <pathogen> via a nasal spray and both arms measures Ig<X> via <text>. One arm then struggles to vigorously eat their own mucus for 24 to 48 hours after infection. One arm struggles to not voluntarily ingest any amount.
We measure Ig<X> in the blood over time and try to see any difference.
The question becomes which Ig<X> to use, at-home tests for IgA might be harder to come by and perform, and labs don’t do them as far as I can tell. Also, IgA responses may linger over time.
IgM response is prompter and dies down entirely once the viruses are gone.
Both have the problem that adaptive immunity will likely kick in faster the second time around someone gets infected.
So the n=1 design here is poor, to get anything concrete we’d need:
Control infection (without mucophagy)
Test infection (with mucophagy)
And we’d be measuring the effect of mucophagy on the adaptive immune response to already sampled viruses, rather than initial adaptive immune response.
Alternatively, we could just get a complete profile of circulating immune cells in the blood, which is expensive but allows us to monitor various non-Ig endpoints, allowing us to spot more fine-grained effects, but also being much more prone to p=hacking.
Finally, the <pathogen> being used here is problematic, I was thinking of a deactivated virus, which in principle can be acquired online as some are used in a variety of experiments. Someone else recommended a bacteriophage or some other virus that doesn’t survive in human cells, but that seems like it’s inviting potential issues and confounding. The one problem, in the Ig testing scenario, is that you’d have to find an Ig test for said virus, ideally from saliva samples.
2 - Sensory Enhancement Behaviour
The other experiment here is to figure out if mucophagy helps sense our environment. The design here is much simpler, buy an air quality monitor and 3 types of incense sticks with similar smells, maybe 3 different brands of rose-smelling incenses or some much.
Have every participant spend 9 days burning an incense stick (there are 3 of each flavor). 1 hour after lighting the stick they will:
Look at which of the 3 incenses the stick had in it
Look at the average TVOC, PM10 concentration, and CO2 (over the elapsed hour)
Either eat or not eat their mucus depending on the group they are part of
Then have every participant spend 9 days doing the same thing, but at the end avoid looking at the stick’s incense type or at the average air quality readings, instead have them guess these first, then write down the real values.
The catch is that participants who engaged in mucophagy in the first 9 days will make these guesses after engaging in mucophagy, and those that didn’t will only have their smell to go by.
We could make this less complicated by dropping the incenses and keeping only the air quality predictions for the first run of the experiment.
This would show some proof for the more boring but easier-to-test hypothesis of mucophagy as aiding the senses.
Will these experiments work? Could I find any subjects willing to spend their time advancing science in this direction? Will I find this utterly devoid of any interest once the comedic novelty of talking to people about it wears off? That I don’t know, but I hope I’ll be able to post a follow-up a year from now.
If any of you have feedback on my experiment design drafts or know someone who knows someone who might know Scott Napper, do let me know.
Related questions to consider: why do cows lick (the inside of) their noses? Which other animals clean their noses in some way and what do they do with what the extract?
This is missing the main factor, IMO, that picking your nose as an adaptive habit isn’t about the eating (a side action), but the picking itself. You introduce pathogens in the environment from your dirty fingertips into the relatively high powered immune region that is your outer nasal channel. Your body gets to learn the baddies that are out there, without exposing itself via higher risk pathways.