How does body hair know it's been cut and grow back?

This question has been answered here:

I have an exception to the rule!

Hair does generally seem to have a growth then a dormant phase, followed by more growth where the old hair is pushed out by a new strand.

However, following a long-term experiment my results are different.

I have one rogue ear-hair.

It grows to a consistent length if left unmolested, and eventually falls out. This concurs with the above theory.

However, if I let it get to it’s full length and allow it to stop for a while, then cut it halfway, it immediately starts growing again to its full length before stopping again.
It’s not a new hair, it’s blunt at the end.

I can cut the strand anywhere along its length and it will grow back to its full length.
If the above thery was correct (that there was a growth phase of a predetermined time) then I could mess with it by cutting the hair when it reaches, say, three quarter length and it should grow back to one quarter length before reaching the dormant phase.
Doesn’t happen. Keeps going.

I can cut the same hair several times and it will continue to grow until it reaches its happy length.

I can leave it for months and it will get to full length and stay there.
As soon as it is chopped to any lesser length, off it goes, growing away!

So, what does everyone think?
There is only one hair, this is not a case of mistaken identity!

First of all, welcome to the message board. That’s a nice first post.

Second, when you are replying to one of Cecils columns, it should go in the forum Comments on Cecil’s columns It will help if you learn the rules for each forum and know which type of message goes where.

Third, congratulations on following the ettiquette and providing a link to Cecil’s column. Many newbies fail to do this and havce to have the rules explained to them. Well done for this.

I’ll move this one to Comments on Cecil’s Columns.

samclem General Questions Moderator

The Dope on this.

What that says, essentially, is that hair grows to it’s maximum length unless shaved or cut. When it reaches that lengh, the hair falls out. Since hairs are surrounded by lots of other hairs, this is not easily noticed. Unless, I suppose, one had a favorite hair.

“I got my hair highlighted, because I thought some strands were more important than others.” - Mitch Hedburg

I must learn t type more quickly. Or perhaps to preview.

Actually what is says is that a hair grows for some period of time then stops, then falls out. This is all managed by the follicle, which is completely indifferent as to the actual length of the hair. If a hair uncut would grow to 2 feet, but you trim it to an inch at the end of the follicle’s growth cycle, it will be an inch until it falls out. Maybe that what you mean.

Notwithstanding the OP’s claims, there is no way for the follicle to know that a hair has been cut. A hair is dead tissue, like a fingernail. No nutrients or information can be transmitted in either direction on a hair.

The OP needs to do a couple of things to make this experiment a little more rigrous. First I would mark the hair in some way, like with a red permanent marker, to absolutely rule out the possibility of mistaken identity. This might start a fashion trend. Second, I would let the hair grow untouched until it falls out, to determine the full growth cycle. Maybe this hair has an anomolously long growth cycle and you’ve never really found out what its true maximum length is. Get back to us in 2-3 years. :smiley:

Hello again.
The hair is alone, it is a lonesome hair. It definitely needs no magic marking. This hair is indubitably identifiable as being the sole strand in an otherwise baldly barren ear.
We’ve grown together. I know it well.

The full growth is approximately 13mm. Several growth cycles have been observed. It will grow, stop, fall out or not depending on its whim. It will eventually give way if hauled by a team of horses. Painfully.

It can be scythed back to 6mm, it will grow back to 13mm. It can be left at 13mm for a month, then cut, it will resume growth and stop again at 13mm.

This has been an ongoing experiment.

I know the theory - the trouble is, my hair doesn’t. You’d think it would listen what with it being in the perfect place for audio.

I think it may have eyes or, at the very least, a basic light sensor. By gaining its optimum length of 13mm it can “see” out of my ear in all directions. Not for it the mere passing glimpse of the vistas to my port side. A full panorama is required.
Perhaps, then, it is a plant. Or does my ear have eyes?

What if it is a sentient being in its own right. Anything could happen now, if it thinks I’m onto it.