"How can you tell if someone's a natural redhead? Operate on 'em! On average, redheads require 20 percent more general anesthesia than non-gingers before going under the knife. Researchers believe that the same recessive gene that causes red hair and fairer skin also affects the brain's pain receptors, making numbing agents such as Novocaine less effective. And because fillings and root canals also involve anesthesia, redheads are twice as likely as others to avoid dental care. For them, a visit to the dentist really is more painful."
from Mental Floss, May-June 2011, p. 14.
