[ELI5] Why do some hairs continue to grow and others don’t?

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For example, head hair seems to grow forever if I don’t cut it, but my arms doesn’t, there’s like a *limit* of growing

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4 Answers

Anonymous 0 Comments

Actually, hairs don’t stop growing. But some hairs are “programmed” to fall out after a while. It’s why you don’t have 6″ eyelashes! Of course, they get replaced by new hairs that grow in.

Anonymous 0 Comments

The average growing cycle of hair is around 6 to 7 years when you don’t cut it and it doesn’t break. You’ll reach, what scientists call, terminal length. It’s the longest a hair can grow. Most people never get to that as nobody grows out their hair for 7 years without cutting it.

And there are various other factors influencing your hair growth.

Anonymous 0 Comments

There isn’t a limit on growing. The hairs on your arms continuously grow. The very tip of your arm hair eventually reaches a point that wear and tear causes it to break off or it may fall out at the root and start over again. Since this eventually happens to all hair after a certain point depending on how long that hair has been growing, it seems like there’s a limit on the length when really it’s the age of the hair imposing that limit.

You may notice that a particularly thick hair, like one growing out of a mole ends up being much longer than the others. This is because it’s thickness allows it to withstand wear and tear longer than the rest of your body hair.

Anonymous 0 Comments

With long head hair you have to coax it because the hair is dead. It relies on oil from the scalp and doesn’t need to be washed daily. I have really thick curly hair almost to my waist now but it used to be unhealthy until I started wrapping it into a bun during a lot of my showers instead of washing it. Brushing distributes the oil and that’s why hair looks the way it does after it’s brushed- shinier and in place.