"We were talking about the different types of molecules that are present in mucus, and it's well known that there's a lot of sugar groups. And then we took it a little bit further and said maybe your mucus tastes sweet to tantalize you to eat it. Kids who sort of don't know any better or know any better that picking their nose and eating it may actually be training their immune system to the different types of pathogens and agents that may be present within the air," Dr. Napper said.