The hair on my head will keep growing forever until i die (unless I go
bald).  On the other hand, the hair on my arms, legs, armpits, and
groin *stops* growing when it reaches a certain length.  Left alone,
this hair will grow to be on the order of 1 inch or two long, then
stop.  If I cut it, it will start growing again until it reaches the
length it was before I cut it.

Some people I have talked to maintain that the armpit hair *does* keep
growing, it's just that it keeps falling out too, so the average
length somehow stays constant if you don't cut it.  But I don't buy
that.

They say that hair is dead, and only the follicle is alive.  If that's
true, how does the armpit follicle know to start growing more hair
when you
cut it?  This also applies to dogs and other animals that have a fixed
coat length.

Is the follicle somehow in communication with the end of the hair that
it is growing?  or what?  :}

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hair knows when to stop growing

Thank you,

jbf777-ga
GA Researcher

Here are two interesting articles about hair growth from the archives
of "The Straight Dope," a site which features entertaining and
informative answers to a variety of questions:

The Straight Dope: How does body hair know it's been cut and grow
back?
http://www.straightdope.com/classics/a1_097b.html

The Straight Dope: Why does head hair grow indefinitely but other body
hair doesn't?
http://www.straightdope.com/classics/a3_044a.html