Here’s what Professor Hallux has to say:
I’m glad you asked. There’s a very simple explanation.
You see, your belly button is like a crinkly crater. Our clothes produce lint – that’s tiny bits that fall off. Some of the lint gets stuck down the crater, and it all joins up to makes the fluff.
Men tend to get more fluff in their belly buttons than women because their hairier tummies can act like a net to keep the fluff trapped. When you shower or bath, most of the fluff is washed clean away.
Belly buttons are of enormous interest to some scientists because they hold all sorts – not just fluff, but interesting bacteria too. A scientist called Rob Dunn found a type of rare bacteria in his belly button that you normally only find on moths and soyabeans.
I wonder what he had been rolling around in?! Hee hee! So a bit of fluff is nothing to worry about – you could even start collecting all the different colours.