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Growing Hair

September 4, 2008

Why all hairs aren’t created equal.


Hair there and everywhere…I’m Bob Hirshon and this is Science Update.

Today’s listener question comes Wela Yong of Iowa City, Iowa. She wants to know why hair on our head grows slowly but very long, while hair on the rest of our body grows quickly but stops at a shorter length. We talked to Paradi Mirmirani, a dermatologist at the Kaiser Permanente Medical Group in Vallejo, California. She says the way that hair grows is genetically programmed into the hair follicle. And that programming differs depending on where the hair is located on the body.

PARADI MIRMIRANI (Kaiser Permanente):
We’ve got some very nice evidence that if you take hair from one part of the scalp, for example, and plant it somewhere else, it still retains the original genetic programming that it came with.

Mirmirani says scalp hair grows for about three years before falling out, but hair located elsewhere falls out much sooner. I’m Bob Hirshon for AAAS, the science society.