Hair has been much on my mind recently, probably because it keeps getting in my eyes. I grow it thick, and I usually put off haircuts until the last minute, so I’ve had plenty of occasion to wonder just what this stuff is that sprouts from our bodies and we spend so much time cutting, conditioning, combing and cussing.

“Hairs,” says the encyclopedia, “are thin growths that protrude like filaments from the skin of mammals.” Only mammals have hair, varying from thick, like sheep, to sparse, like elephants, to almost non-existent, like whales and Star Trek‘s Captain Picard.

Hair performs many functions. Animals with lots of it usually need it for insulation. Special facial hairs called vibrissae (or “whiskers,” though our own whiskers aren’t vibrissae), serve as touch organs. Hair can camouflage: the spots of a leopard make it hard to see among the shifting shadows of leaves, and the fur of rabbits changes from dark in the summer to snow-white in the winter. Patterns of hair growth may distinguish the sexes: the beards of men and the manes of lions. And hair can even help an animal defend itself: porcupine quills are hairs, and the horn of the rhinoceros is made of hair.

In addition, hairs in particular body regions may have specific functions. For example, touching the eyelashes triggers nerve circuits that close the eyelid.

Hair grows out of “follicles” located in the epidermis, or top layer, of the skin. Sweat glands lubricate the hair, and “sebaceous” glands give it a waxy coating that keeps it from drying out (and makes unwashed hair oily.) Every follicle also has a tiny muscle which raises the hair in response to fear or cold. If we had enough fur, this would make us fluff up to look bigger and feel warmer. As it is, it just makes us look like plucked waterfowl.

Like skin, hairs are living parts of the body, made up of three layers of cells, some alive, some dead. The middle layer gives hair its shape and hardness, accumulating keratin, the same protein scales, feathers, nails, hooves, claws, horns and the outer, waterproof layer of skin are made of. Hair colour, which ranges from yellow to black, comes from melanin, the same pigment that colours our skin. When the melanin-making cells die, hair emerges without pigment: gray. The shape of the hair determines how it grows: the flatter the hair in cross section, the curlier it is.

Here’s an unsurprising bit of data: hair is not permanent. Hair follicles alternate growth phases with rest phases with shedding phases (where they get rid of the current hair and start a new one). A human scalp hair usually lasts about four years.

Some animals shed most of their hair at once, usually seasonally, but human and cat follicles seem to have independent cycles. In other words, we both shed all year long.

Some people shed hair that never comes back: they go bald. Most common is pattern baldness, a hereditary trait that shows up in men more than women because it’s influenced by testosterone. No hair tonic or medical measure can prevent or reverse it.

Premature baldness, however, can result from many things, from typhoid fever to stress to nutritional deficiencies to radiation to chemotherapy. To combat it, plugs of hair-containing skin from the back of the head, or even individual follicles, are sometimes successfully transplanted on bare areas of the scalp. Recently, the hypertension drug minoxidil has had a lot of press as a hair restorer, but it’s expensive, must be used daily, and seems to work mainly on young men who’ve only just begun to lose hair.

On the other end of the scale is hirsutism, an excessive growth of hair. Unwanted hair may be bleached or temporarily removed through shaving, waxing, plucking or chemical warfare, but the only permanent solution is electrolysis, in which the hair root is destroyed by an electrical current transmitted through a slender needle.

Usually we don’t want our hair removed, just groomed, for which we turn to a barber, a person serving in an occupation that might be the world’s oldest, if that title weren’t reserved for something else. At one time, barbering was allied with surgery; in fact, the striped red-and-white barber’s pole signifies blood and bandages. (This is not something to share with a small boy already unhappy with the idea of getting his hair cut.)

In the U.S. there are more than 160,000 barbers and barbering is a $1 billion-a-year business. I think it’s about time I did my bit to help Canadian barbers catch up.

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