The nature of navel fluff

I've been a prodigious producer of navel fluff for as long as I can remember. In fact I've considered saving it to figure out how much I produce in a year, and whether it's enough to fill a pillow. But it looks like someone beat me to it, and published it in one of my favorite journals "medical hypotheses". I have noticed that no woman I've known produces belly button lint which made me think you needed some belly hair and a belly button with a lip to accumulate the lint. Turns out I was bang on:

"Med Hypotheses. 2009 Jun;72(6):623-5. Epub 2009 Feb 23.
The nature of navel fluff.

Steinhauser G.

Vienna University of Technology, Atominstitut der Osterreichischen Universitäten, Stadionallee 2, 1020 Vienna, Austria. georg.steinhauser@ati.ac.at

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."