Navel lint (also known by names such as navel fluff, belly button lint, belly button fluff, and dip lint) is an accumulation of fluffy fibers in the navel cavity. Many people find that, at the beginning and end of the day, a small lump of fluff has appeared in the navel cavity. This lint is an accumulation of cloth fibers that are scraped by body hair. The reasons for its accumulation in the navel are a subject of speculation. A likely hypothesis is that rubbing of navel hairs and clothing contributes to a build-up of static electricity resulting in the collection of clothing fibers and to a lesser extent, dead skin cells.
Georg Steinhauser, a chemist writing in the journal Medical Hypotheses said that small pieces of fluff first form in the hair and then end up in the navel at the end of the day. He further said that abdominal hair often seems to grow in concentric circles around the navel, the scaly structure of the hair enhances the abrasion of minuscule fibres from the shirt and directs the lint towards the belly button. Steinhauser established that shaving one's belly will result in a fluff-free navel but only until the hairs grow back. His other suggestions include wearing old clothes, as they tend to shed less lint than newer garments, which can lose up to one thousandth of their weight to the belly button over the course of a year. A body piercing can also be used, with belly button rings particularly effective at sweeping away fibres before they lodge.