[sci.med] Hair growth

mark@cci632.UUCP (Mark Stevans) (05/11/87)

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

ir489@sdcc6.UUCP (05/11/87)

I have noticed that shaved hair grows back longer or thicker, what
causes this?

bhayes@cascade.UUCP (05/12/87)

In article <1215@cci632.UUCP> mark@cci632.UUCP (Mark Stevans) writes:
>[...]
>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.
>					Mark Stevans
>					cci632!mark

I cannot explain the "beard myth", but do believe it.  Several years
ago, I had the honor of being selected to receive a hernia and its
associated operation.  Only minutes before the operation I saw, through
a cloud of Valium, my surgeon quickly shaving my groin.  But for the
Valium this might have been upsetting.  After the operation, through a
cloud of pain, I saw that he had shaved only half my groin.  To this
day the hair grows thicker on that side.  This observation has been
confirmed by a few independent witnesses.  [Sigh.]  

  Barry "you want me to lift a WHAT?" Hayes

hitz@mips.UUCP (05/13/87)

In article <1215@cci632.UUCP> mark@cci632.UUCP (Mark Stevans) writes:
>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.

On a dare I once bleached my hair and eyebrows.  I got an unexpected
lesson in hair growth.

Eyebrows grow much more quickly than head hair so it was easier to see
what was going on.  Almost immediately there were several eyebrow hairs
that were half brown and half blond.  During the next few weeks
completely brown hairs started growing in -- making a sort of "salt and
pepper" effect -- until eventually all the blond was gone.

This seems to support your theory of grow/wait/fall out.
-- 
			Dave Hitz

UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!hitz 	DDD: hitz@408-991-0345