There are two crucial things you need to know about the lint that forms inside of belly buttons. The first is that it’s referred to more scientifically as “navel fluff,” though occasionally those writing about in scientific literature call it belly button lint (BBL). The second is that navel fluff forms more often in middle-aged, hairy men, especially ones who have recently put on weight.
These are the findings of a University of Sydney researcher named Karl Kruszelnicki. Dr Karl, as his fans know him, has an Australian science radio show, and one of his listeners wrote in asking where navel fluff comes from and how it forms.
Navel Displacement Causes, Symptoms and Treatment
That inspired Kruszelnicki to distribute a survey online, which led him to the conclusion that BBL is an affliction mainly of middle-aged men with sufficient body hair. For his research, Kruszelnicki received an Ig Nobel Prize in 2002, an accolade given for research that “first makes you laugh, and then makes you think.” BBC