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!