The nature of navel fluff

Summary

Hard facts on a soft matter! In their popular scientific book (Leyner M, Goldberg B. Why do men have nipples – hundreds of questions you’d only ask a doctor after your third martini. New York: Three Rivers Press; 2005), Leyner and Goldberg raised the question why “some belly buttons collect so much lint”. They were, however, not able to come up with a satisfactory answer. The hypothesis presented herein says that abdominal hair is mainly responsible for the accumulation of navel lint, which, therefore, this is a typically male phenomenon. The abdominal hair collects fibers from cotton shirts and directs them into the navel where they are compacted to a felt-like matter. The most abundant individual mass of a piece of lint was found to be between 1.20 and 1.29 mg (n = 503). However, due to several much larger pieces, the average mass was 1.82 mg in this three year study. When the abdominal hair is shaved, no more lint is collected. Old T-shirts or dress shirts produce less navel fuzz than brand new T-shirts. Using elemental analysis, it could be shown that cotton lint contains a certain amount of foreign material, supposedly cutaneous scales, fat or proteins. Incidentally, lint might thus fulfill a cleaning function for the navel.

Introduction

“By the way, doctor, why do I always find fuzz in my belly button but my wife and her brother do not?” Is not it peculiar that some simple medicine-related questions from everyday life have not yet been answered? Mark Leyner and Dr. Billy Goldberg dedicated their writing efforts to answering exactly such medical questions. The result of their oeuvre was a huge success – their popular scientific medical book “Why Do Men Have Nipples” [1] became a global best seller. The question above attracted the attention of this article’s author, because, though simple, even Leyner and Goldberg were not able to come up with a satisfactory explanation to it:

“One question that cannot be answered, however, is why some belly buttons collect so much lint” [1, p. 57].

The accumulation of navel fluff is probably a widely spread phenomenon. Nonetheless it is an intimate question, thus indeed “you’d only ask a doctor after your third Martini” (the subtitle of [1]) about this topic. The question of the nature of navel fluff seems to concern more people than one would think at first glance. Even the famous journal Nature dedicated some of its precious publication space to an anonymous author’s photograph series entitled “Another matter: Navel fluff” [2]. Three “types” of fluff were shown, from a sailor (“while at sea”), a farmer and an architect. Obviously, these photographs should only attract the reader’s attention. Coincidence or not – these are what one would regard as overwhelmingly male professions. Accordingly, and to the author’s personal experience, navel lint seems to be a phenomenon that affects primarily male adults. Maybe the answer to the introductory question is much simpler than one would expect.