Hair 101: What exactly is hair?

Most people have no idea what really lurks beneath their hair,
unless they’ve been shaving it off already.
For something that you play with, obsess over, color, cut, and twist
into odd shapes, hair is surprisingly dead. Yes, the hair you think
looks so vibrant and alive is actually not alive at all. I’m not saying
that you should ignore or mistreat your hair. For something that’s
dead, hair is quite capable of responding to good treatment or bad.
Hair is technically part of your skin, although like fingernails and
toenails, it grows and separates from your skin. The average head
contains around 100,000 hair follicles, and your entire body is
home to around 5 million hair follicles. Most of the complex activ-
ity that keeps your hair growing goes on below the surface.
The active growth phase of a hair follicle, called the anagen phase,
averages around three years. At any given time, about 90 percent
of your hair is in the anagen phase, and the other 10 percent is
taking a rest in the telogen phase, which is the resting phase, and
disappears from your head.
Hair grows about
1
⁄2 inch a month (although it certainly seems like
more when you need a haircut!) and grows to a length of 11
⁄2 to 3
feet before growth stops and the hair falls out. (In Chapter 2, we
tell you all you ever wanted to know about hair, right down to its
roots.)