October 11, 2011 7:17 PM Subscribe
Why does hair "know" when to stop growing?
posted by arveale to grab bag (11 answers total) 3 users marked this as a favorite
So hair on you head and face (for men) grows quite long, but hair elsewhere stops after growing a specific length. My armpit hair is longer than my arm hair, which in turn is shorter than my leg hair. COOL.
What is the mechanism that "tells" hair when to stop growing? If I were to shave my arm, the hair would "know" and grow back to normal arm hair length, but no longer. Does head hair have the same "off-switch" at some point? HOW DOES IT KNOW?!