Naked Science Forum

General Science => General Science => Topic started by: Melissa Mencini on 19/12/2008 09:38:50

Title: Why does hair stop growing at a certain length?
Post by: Melissa Mencini on 19/12/2008 09:38:50

Melissa Mencini  asked the Naked Scientists:

Hi Chris, Hi Kat,
 
First of all, I want to thank you for putting together one of the smartest and entertaining shows (http://www.thenakedscientists.com/HTML/podcasts/) around. I discovered you about a month ago and I'm pretty sure all of my friends and family are sick of hearing me talk about you guys all the time.

I hope the show (http://www.thenakedscientists.com/HTML/podcasts/) never goes off the air!

My question is about body hair. How does hair on certain parts of your body know to stop growing when it has reached a certain length? For example, if I let my armpit hair grow out it will stop at a certain length and if I were to trim it down a bit it would start to grow back...how does it know that you trimmed it and why doesn't the hair on your head do the same thing???
 
Thanks,
Melissa in Montana

What do you think?

Title: Why does hair stop growing at a certain length?
Post by: ukmicky on 19/12/2008 21:51:42

Hi Melissa

I believe each individual hair follicle goes through a growth cycle switching form being active when they produce hair and inactive when they turn off and don't produce growth.
During the inactive period hairs will fall out and break but you don't notice this as other follicles will still be in their growth cycles.

Also different types of body hair will have different speeds at which it grows and differing strengths preventing it from splitting and breaking to early.

Hopefully someone full of follicle knowledge and not follicularly challenged will come on and either confirm or not confirm my answer

Title: Why does hair stop growing at a certain length?
Post by: erickejah on 25/12/2008 18:17:45

Hello, i could not find anything about a natural trigger that stops the hair from growing, never the less i found an article about decreasing the rate in which hair growths. It may help to correlate structures that alter that process.

Quote

Hate to shave? A Dutch electrical-goods manufacturer is working on a process that uses near-infrared light to cause hair follicles to go dormant for weeks at a time. A device using a halogen lamp emits 15-millisecond pulses of light in the 600- to 950- nanometre wavelengths. By moving the device slowly over the skin, a user can force hair follicles into a "telogen phase," in which they temporarily stop producing hair.

"NOW YOU CAN PUT YOUR BEARD TO SLEEP." Maclean's 120.1 (15 Jan. 2007): 44-44. Academic Search Premier. EBSCO. [Library name], [City], [State abbreviation]. 25 Dec. 2008 <http://wf2dnvr15.webfeat.org:80/IDlFL153/url=http://search.ebscohost.com/login.aspx?direct=true&db=aph&AN=23707374&site=ehost-live>.

Title: Why does hair stop growing at a certain length?
Post by: yor_on on 31/12/2008 10:43:43

Kind of neat erickejah.

Does this mean that I could start to hear what people say again?