IgNobel (3): navel-gazing

This year's IgNobel judges honoured a study of belly-button lint.

Call it the “belly-button lint sign.” If you're examining a patient and encounter an umbilicus that looks like the lint trap in your dryer, chances are the patient is male, middle-aged and hairy. It can also be a sign that the patient is putting on weight.

These are the findings of a massive survey of belly-button lint (BBL) conducted by Dr. Karl Kruszelnicki of the University of Sydney, who won the coveted IgNobel Prize for Interdisciplinary Research (see www.improbable.com).

A first in the world, the BBL survey was inspired by real questions called in to “Dr. Karl's” science radio show. “Why is my belly-button fluff blue, and why do I get it?”

It turns out that no one knew the answers, so the intrepid Aussie researchers rose to the challenge. In addition to a Web-based survey, researchers collected samples and asked participants to shave their belly hair to see if it stopped lint from collecting. Lint was examined under an electron microscope.

While the results were not entirely definitive, they did provide support for Dr. Kruszelnicki's working hypothesis. BBL is believed to be made from clothing fibres, as well as some hair and skin cells. Belly hair is believed to act “like a one-way ratchet mechanism,” pulling fibres into the navel. Indeed, many of the experimenters found that shaving around the navel stopped the accumulation of BBL.

The colour question remains unresolved. A lot of people notice that their BBL is blue, although they may not wear blue. Theories about the blue shift include the colour of laundry detergent, the colour of clothing dyes and the presence of urea in sweat. One respondent speculated that BBL begins to compost in the navel, turning different colours as it disintegrates.

A man named Graham Barker has collected his BBL since 1984, filling three large bottles and earning him a place in the Guinness Book of World Records. — Carolyn Brown, Ottawa, Ont.