Natural red hair is exceptionally rare, seen in fewer than 2% of the global population. Interestingly, the same genes that give rise to red hair also influence how redheads perceive and handle pain.
According to Dr. Shalini Shah, a pain management specialist at UCI Health, classic anesthesia studies have found that redheads typically need higher anesthesia doses. Moreover, recent research suggests that redheads exhibit greater tolerance to local anesthetics and heightened sensitivity to opioids.
Redheads Perceive Pain Differently
A 2023 review in the journal Anesthesiology and Perioperative Science delves into the intriguing relationship between red hair and pain sensitivity. Anecdotal evidence from anesthesiologists and a variety of animal and human studies have suggested that redheads may exhibit different responses to both pain and pain-relieving medications.
This connection is far from straightforward, as co-author Jaideep Pandit, a consultant anesthesiologist at the Oxford University Hospitals NHS Foundation Trust, explained. Past research has explored various forms of pain, leading to some ambiguity regarding how redheads' pain experiences differ.
Certain studies have indicated that redheads might be more sensitive to specific types of pain while showing different responses to others. For instance, one study revealed that redheaded women exhibited heightened sensitivity to temperature-related pain, with the nerve blocker lidocaine being less effective for pain management in redheads compared to individuals with dark hair.
On the other hand, another study found that redheads were less sensitive to pain induced by electric shocks compared to those without red hair. As for the link between red hair and pain management, there is evidence indicating that redheads require 20% more general anesthesia for sedation and more local anesthesia to mitigate pain.
However, redheads are also found to be more sensitive to certain opioids, including mu-opioids like morphine and fentanyl, although this effect might be specific to female patients. It's worth noting that, in 2015, a study discovered no discernible difference between redheads and others in their responses to anesthesia or pain medications, making the data somewhat inconclusive.
Dr. David Fisher, the chief of the dermatology department at Massachusetts General Hospital, conducted a 2021 study on pain in red-haired mice. His findings indicated that red-haired mice, much like red-haired humans, appear to experience a delayed perception of pain as if they are somewhat numb to it initially. However, once the pain reaches a higher threshold, redheads feel it more intensely than those without red hair.
Genetics and Pain Perception of Redheads
Understanding the unique pain experience of red-haired individuals has been challenging due to the complexities of human genetics. To investigate this, Dr. David Fisher and his team conducted studies with mice, which offered precise genetic control.
While most red hair results from mutations in the MC1R gene, controlling the genes of mice that either carried red or black hair variants but produced no pigment allowed researchers to observe distinct differences in pain thresholds between the two groups.
The explanation for this lies in the MC1R gene's impact on melanocytes, responsible for pigment production. The MC1R variation in redheads not only affects melanocyte proteins but also reduces the production of POMC, a substance that influences pain sensitivity and opioid responses by regulating specific receptors.
While the advantage of red hair in northern latitudes, where it enhances ultraviolet absorption for vitamin D synthesis, is understood, the potential evolutionary advantages of altered pain perception and opioid sensitivity in redheads remain unclear. This link between red hair and pain could eventually aid doctors in predicting individual responses to pain and pain medications based on genetic factors.
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