Mucophagy (literally mucus-eating, also referred as picking one's nose and eating it) is the consumption of the nasal mucus, boogers, and other detritus obtained from nose-picking.
Modern scientific research suggests that mucophagy seems to be a natural and even healthy activity, which exposes the digestive system to bacteria accumulated in the mucus, thereby helping to strengthen the overall immune system.
The body even naturally encourages the formation of a dense, salty coating to the boogers to make them more palatable. There is no other known reason for the high salt content in the mucus in the nose.
In mankind's caveman times - it would not have been strange to spend an evening sitting around with friends and sampling each other's boogers. It sounds disgusting - but its simply part of our instinctual primate grooming behaivors that have only recently been repressed through collective social training.
Studies done on dozens of feral human children found in the wild and raised by animals (and possessing no knowledge of modern social mores) show that they all spent at least a part of each day carefully clearing out their nostrils and consuming the boogers. It SOUNDS bestial and ignorant to us today - but Mother Nature (or God) always has a very good reason for putting non-learned, instinctual behaivor like this into our brains from the get go...
It has been speculated that the reason why humans have become so susceptible to viruses and bacterial infections in the last 500 years or so is indeed, because we have lost this beneficial, immune system strengthening behaivor.