It’s one of the most easiest procedures for dental students to master, yet somehow anesthesia works different on most people. Why? Does the difference come from height? Weight? Hair colour?
How about hair colour?
Some people have a rare variant of something called the ‘MC1R’ gene, that has been directly correlated with being more sensitive to pain and discomfort, which makes them more difficult to anesthetize.
While there is currently no gene mapping option to find this variation and predict this abnormal tolerance, this gene produces the melanin responsible for hair colour and skin tone – these pain-intolerant people may be more easily identified by observing the colour of their hair, and fair skin tones. While blond, brown and black-haired people produce melanin, those with red hair have a mutation of this receptor. It produces a different colouring called “pheomelanin,” which results in freckles, fair skin and red or orangish hair. About 5 percent of people with western-European heritage are estimated to have these characteristics.
Two studies were conducted that compared to blondes and brunettes, redheads. The results showed that redheads were more resistant to the effects of local anesthesia, and requiring an average of up to 20% more general anesthesia. In addition to being weary of delivering enough local, we as dentists need to be cautious of the fact that past experiences of failed local anesthesia causes extreme dental anxiety in patients. Because of this, redheads are twice as likely to avoid dental care than individuals who have darker hair colours.