Blonds have more fun. Redheads are harder to numb. No, this is not a nursery rhyme; it’s science.
I perform about 10 biopsies every day. That’s 50 times every week or 2,500 times every year that I numb people up. There are two things I know for sure: 1.) 1% lidocaine with epinephrine works instantly and completely to numb the skin. 2.) There is a tremendous amount of variability in people’s pain threshold.
If you have ever wondered why you feel pain when a doctor or dentist numbs you for a procedure, then take a look in the mirror. Your red hair might be the reason for your pain.
It is not that redheads are wimps or even that redheads are especially sensitive to pain. It is that redheads seem to be resistant to the numbing effects of lidocaine. Anesthesiologists at the University of Louisville in Kentucky did a study to determine pain sensitivity in red-haired women as compared to dark-haired women after their skin was numbed with lidocaine. They tested both topical lidocaine cream and injections of lidocaine. Both groups had the same amount of numbing medication. They then subjected the volunteers to painful stimuli such as mild electroshocks, intense cold, and intense heat.
The results: the redheads were more sensitive to pain as compared to the dark-haired women. What is the cause of this disparity (other than the theory that redheads’ parents are too soft on their kids growing up)? Red hair occurs mostly in people of Northern European descent. It is the result of a mutation in a receptor called the melanocortin-1-receptor (MC1R). As a result, people with red hair make pheomelanin instead of eumelanin. Pheomelanin is reddish or copper as compared to eumelanin which is brown or black.
Although it is not clear, it seems that the MC1R mutation in redheads leads not only to red hair, but also to differences in pain sensitivity in the brain. These differences become apparent when we try to suppress noxious stimuli with local anesthetics as well as with general anesthesia in the operating room. The good news is that although there do seem to be real differences in pain sensitivity, the differences are small, and it is certainly still possible to adequately and completely numb the skin of people with red hair.
“But what about blonds?” you ask. Unfortunately the researchers could not look at blonds in this study. Apparently they all got lost on the way to the experiment.
Photo: Vincent Boiteau (flickr)