Body Hair Does So Much More Than You Thought

Watch a fly land on the kitchen table, and the first thing it does is clean itself, very, very carefully. Although we can’t see it, the animal’s surface is covered with dust, pollen and even insidious mites that could burrow into its body if not removed.

Staying clean can be a matter of life and death. All animals, including us human beings, take cleaning just as seriously. Each year, we spend an entire day bathing, and another two weeks cleaning our houses. Cleaning may be as fundamental to life as eating, breathing and mating.

Yet somehow, cleaning has gotten little attention.

In our new review article in the Journal of Experimental Biology, we discuss how cleaning happens in nature and whether animals indeed have principles for getting clean. We looked at microscope images to count the number and sizes of hairs across hundreds of animals. We read nearly a hundred articles on cleaning in nature, trying to put numbers onto the cleaning process.

Extrapolating principles is an important step for science, and even more necessary for engineering. Learning better ways to clean will not just allow us to understand the humble fly, but also to build new kinds of devices that stay clean longer.

Hair vastly amplifies a body’s surface area

To understand how animals get clean, one must first understand how they get dirty. Dirt accumulates on an animal’s exterior just as a consequence of living life. The surface area of an animal is not as easy to figure out as measuring the dimensions of a cardboard box. Most animals – from mosquitoes to elephants – are hairy. Beyond the exterior of a creature’s skin, hairs provide further surface area where dirt can accumulate.

We found that on average, hair increases an animal’s apparent surface area by a factor of a hundred. Thus, —> Read More