Does Hair Ever Stop Growing?

Have you ever wondered why the hair on your head will continue to grow, but your leg hair doesn't? Join Hank Green for a new episode of SciShow and discover the answer!
----------
Dooblydoo thanks go to the following Patreon supporters -- we couldn't make SciShow without them! Shout out to Christopher Prevoe, Justin Ove, John Szymakowski, Peso255, Ruben Galvao, Fatima Iqbal, Justin Lentz, and David Campos.
----------

Or help support us by becoming our patron on Patreon:
----------
Looking for SciShow elsewhere on the internet?

[ugoleftillgorite]

Now if we could just find a way to get our lawns to do the same thing.

[lina]

if only the hair knew not to grow after it gets pulled out 50 times

[Theodora]

Why are there different hair structures ( wavy, curly, straight, thin, thick)

[LucysCorsetry]

One example of uncontrolled growth of keratin structures is the "Feather Duster" budgie (feathers are beta-keratin structures as opposed to our hair which is alpha-keratin, but their growth and moulting process isn't too different from our hair growth phases). One of the reasons that the budgies have a significantly shorter life span is that the excessive feather growth leaches nutrients from the rest of the body.

[Coconutsales]

OH! Explain why certain follicles contain up to two to three strands of hair! (Lots of people's legs generally have two hairs popping out of a single follicle.) That would be really interesting!

[nightshadedapple]

You know, a few days ago, I was shaving my face and began to wonder about what causes some hair to grow indefinitely, while others reach a limit. I thought to myself, "I wish SciShow would do an episode on this topic". And here we are...
Conclusion? SciShow should do an episode on synchronicity and the Baader-Meinhof phenomenon.

[ljmastertroll]

Why can't I grow a rhinoceros horn?

[jayk]

When does pubic hair stop growing? I'm getting carpet burns every time I scratch my balls

[Nihilnovus]

I want to know why do we go bald and before I get there how to prevent it...

[AShoutIntoTheVoid]

I was just talking with a friend about this the other week! Great coincidence. This is far more clear and concise an explanation than what I found when searching. Thanks Hank!

[skrdman]

There's a lot of good information here, but I still wish we knew more. It'd be nice to have more control over our hair growth.

On the other hand, there's a healthy discipline in knowing that there are some things we can't, and probably shouldn't, control, even if we want to.

[meaganmutuc]

this gives me a better understanding of how hair works thanks

[daniabadeister]

1, 25cm A MONTH!?
It takes my hair like 6 months to grow 1cm wtf

[danieltsmoke]

Holy crap, I was just wondering this!!

[Wildlon]

Literally love Hank so much, for no reason other than his glasses are adorable

[AlphaBetaDeltaGamma]

you have some sexy eyebrows, Hank. I'm really glad you showed that closeup

[Yourmanjeff]

Never really actively asked myself that question, but I have always wondered. Another excellent episode.

[KeithSwanger]

Very interesting. Since we know these hair phases, I wonder how long it will take to develop some sort of skin cream that keeps hairs in the telogen phase. Not having to shave sounds pretty great to me.

[Nanenna]

As someone who's recently turned 30 I've noticed (and my husband has noticed for his own hair) that some eyebrow hairs grow really long now. I wonder what it is about aging that changes the growth cycles for eyebrows? (The stereotype of old people having long, long, long eyebrows is based on truth, afterall.)

[crystalallen]

Ive never seen my skin hair fall out... never