The average man is home to 1.8 mg of belly button fluff at any one time, and it’s almost always blue. What is this mysterious substance, and why does it gather there?

Inspired by literal navel gazing, Dr Georg Steinhauser spent three years of his life examining belly button fluff, cataloging 503 individual examples of the phenomenon, and asking his friends and family about the contents of their navels. In addition to being banned from further dinner parties, he discovered that a previously unknown type of hair was the culprit. This particular hair is not only unusually fine, but has tiny little barbs on it that rub on clothes and knock small amounts of cotton off. Their arrangement—concentric circles—act almost as a funnel, bringing these small pieces of fluff inwards, collecting as they enter the navel.

However, the navel is not just a home for unwanted bits of t-shirt. As an area with a large number of skin folds, not to mention a deep crevice, it is a trap for all sorts of dead skin, discarded fat molecules, bits of dust and assorted scales and proteins. Thus, that benign ball of fluff is in fact largely bits of you.

Armed with this rampant speculation, Dr Steinhauser hypothesized that the specialized fluff-catching hairs were in fact a deliberate attempt by the body at cleaning itself. Rather than allow the dead skin and other human detritus to fester and become a feasting ground for bacteria, the body uses available cloth to create an enticing object for human males to remove and flick away. This makes belly button fluff analogous to dried nasal mucus in more ways than one.

As for the question of why it is blue, that is something of a mystery.

One theory is that the blue dye common in garments such as jeans ends up dying everything in the belly button blue. Even items of clothing that aren’t themselves blue may contain blue components in the makeup of their dyes, and this somehow dominates all other colors, like that blue towel you accidentally put in with the white washing.

That is, unless you are an Australian hospital worker called Graham Barker. He claims his navel lint is red, despite rarely wearing any red clothing. And this man is definitely an expert on the matter. Mr Barker has meticulously collected and labeled his belly button deposits every day since 1984, earning him a place in the Guinness Book Of Records.

If you are not inclined to catalog your fluff as Graham Barker is, then you might want to try reducing your capacity for gathering dust. The obvious solution is to shave your belly, although that is a temporary solution as the barbed hairs quickly grow back, as Dr Steinhauser discovered when he attempted the procedure on himself. The other solution is to minimize the amount of available lint, which can be achieved by wearing worn and old clothing, rather than new clothes. Having said that, you can’t keep wearing the same clothes forever, so what else? If you don’t mind a bit of modification, a belly button ring apparently works wonders.

There is another preventative measure, however. In a separate study conducted by Australian researchers, they identified being slightly overweight as a significant risk factor. So, you can either lose weight, thus providing a smaller surface area for your clothes to rub against, or you can gain weight, at which point you stop collecting belly button fluff and start gathering other things, like cheese sandwiches and small children.

And if you think all this is a bit too much contemplation of the navel, Dr Steinhauser has a word for you. "The question of the nature of navel fluff seems to concern more people than one would think at first glance.”

This article originally appeared on mental_floss UK.