Laura loves this article as it justifies what she's always known.  I like it because it says she has a "defect" :)

And just in case the image doesn't come through clearly:

It used to be that "only your hairdresser knows for sure" whether you color your hair, but redheads can now include their anesthesiologist.  A recent study showed that natural redheads need 20 percent more surgical anesthesia than do women with other hair colors.
Dr. Daniel Sessler, a professor of anesthesiology at the University of Lousiville, said he and his colleagues scientifically proved what anesthesiologists long have noticed in the operating room: that redheads seem to require more anesthesia.
To test their theory, Sessler and his co-workers induced general anesthesia in 20 healthy women - 10 with naturally bright-red hair and 10 with dark hair.  They then observed how the subjects responded to a pain stimulus.  Depending on the pain response, the anesthesiologists raised or lowered the dose of desflurane, a common inhaled anesthesic, until the ideal dose was reached.  Redheads needed significantly higher doses than either the dark-haired subjects or the few blondes the researchers tested.
One explanation why carrot-tops need stronger anesthesia is that they possibly have greater pain sensitivity.  They have a defect in the "melanocortin-1 receptor," which makes red pigment instead of the normal dark pigment (melanin) for hair.