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From: mark@cci632.UUCP (Mark Stevans)
Newsgroups: sci.med,sci.bio
Subject: Hair growth
Message-ID: <1215@cci632.UUCP>
Date: Mon, 11-May-87 00:48:14 EDT
Article-I.D.: cci632.1215
Posted: Mon May 11 00:48:14 1987
Date-Received: Wed, 13-May-87 00:41:06 EDT
Organization: CCI, Communications Systems Division, Rochester, NY
Lines: 28
Keywords: hair grow cut shave follicle
Xref: mnetor sci.med:1894 sci.bio:343

I have a question concerning hair growth.  A friend believes that each
hair follicle must know how long its associated hair is, and/or if
the hair has been cut or shaved.  I believe it does not.

I postulate that, each follicle operates on a cycle: extrude hair for A
days, stop for B days, throw out the hair, wait C days, and repeat.  The
value of A, B, and C depends on the individual, and the location of the
follicle (e.g. facial, leg, scalp, etc.).  I believe that none of this
is affected by what you do to the hair, except maybe by pulling it out
forcibly "by the roots", which may irritate the follicle into doing
something special.

She asks why, if she shaves her legs, it appears that the hair all starts
growing until it gets back to the unshaven length.  My explanation is that
about 1/3 of the follicles are in the growing stage at any point in time,
so if you shave, wait a week, and look closely, you will note that 2/3 of
the shaved hairs remain shaved, and 1/3 have a week of growth.  These 1/3
will grow out to their maximum length, being joined along the way by
formerly dormant follicles, so it only seems like they all started
growing as a response to being cut, grow out to the old length, and stop.

My hair follicle model counters the beard myth: many people believe that
if you shave, your hair grows faster.  I, personally, do not think so.

Does anyone care to divulge the canonical hair growth story?

					Mark Stevans
					cci632!mark