how do your eyebrows, eyelashes, etc know when to stop growing?
Question:
Answers:
Genetics plus environment.
When a cell develops into an eyelash or eye-brow cell, a "lengh to grow" gene (or two or three) is turned on as part of being such a cell. The thickness of the eyelashes is determined by yet another gene. The curliness of the hairs, shape of the brow and color are all determined by their own genes. So far as I can tell, no one has identified the specific gene(s) for lash length. The priority is on identifying disease genes, instead of traits.
Genetically, family with allergies frequently have long eyelashes, a condition call trichomegaly.
Environmentally, some medications cause the eyelashes and brows to lengthen or shorten. In some people, warm temperatures caus eyelash and brows hair to lengthen, compared to cool temperatures.
Other Answers:
it's programmed into your DNA like everything else, how do cells know when to stop multiplying, how do your cells in your eyes know what pigment to make, its all in DNA
As you get older hair growth also slow down as well. Waxing multiple times can get certain area to stop growing.
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