Before administering anesthesia, doctors carefully evaluate the patient's general health, physiology, and medical history to determine the safest and most effective approach. However, beyond factors such as age or weight, one unusual feature has long piqued the curiosity of patients and doctors alike: red hair.
For years, anecdotal reports have suggested that people with naturally red hair experience pain differently and may require altered doses of pain medications or anesthesia. Read on to find out what the science actually supports and where the evidence is lacking.
Read more: Female hormones help the body produce its own opioids, which help cope with pain.
The Gene Behind the Difference
Naturally, red hair is rare, occurring in less than 2 percent of the world's population. Its characteristic color is associated with variants in the melanocortin-1 receptor (MC1R) gene. The gene is best known for determining hair and skin pigmentation, ultraviolet sensitivity and melanoma risk, but it also appears to play a role in how the body processes pain and responds to certain medications, according to UCLA Health.
Anesthesia allows procedures to be carried out safely and humanely. But how anesthetics interact depending on a person's genetic makeup remains an active area of ​​research. Individuals with MC1R variants appear to demonstrate differences in pain sensitivity and response to both local and systemic anesthesia.
Understanding these differences is important. If some patients predictably respond differently to anesthetics, physicians can adjust protocols to improve comfort and safety. Although we haven't gotten there yet, the genetic link offers a compelling explanation for the long-standing debate about red hair pain.
Different perceptions of pain, responses to opioids and local anesthesia
Studies of pain perception and response to medications in redheads have produced mixed but intriguing results. 2022 Study in Pain suggests that red-haired women may be more sensitive to certain types of pain, such as pain associated with cold.
However, research in Journal of Medical Genetics found that redheads tolerated electrical stimulation-induced pain better than non-redheaded controls. Overall, there were also strong differences between the sexes.
Response to medications also varies. Research suggests that variants in the MC1R gene may influence redheads' response to analgesics, although the effect is not consistent across genders and drug types. Research from PNAS found that red-haired women responded differently to κ-opioid painkillers, while Journal of Medical Genetics have shown an increased response to μ-opioids (morphine-like drugs) in MC1R variant carriers, regardless of gender, although further studies may be required.
Local anesthesia may be where the differences are most noticeable. Several studies, including one in Anesthesiology, reported reduced efficacy of lidocaine injection in red-haired participants compared to dark-haired participants. The response to general anesthesia and sedatives is less predictable, with some studies suggesting the need for higher doses and others finding no difference at all, according to studies Springer Nature Link And Anesthesiology.
Overall, MC1R variants appear to influence pain and response to medications, but results remain inconsistent, researchers from Sweden concluded in a review published in May 2024.
Evidence not yet established
Despite the intriguing findings, clear conclusions remain unclear. Many studies included small sample sizes, making it difficult to generalize the results. Researchers reviewing this body of work often call for larger randomized trials with improved designs.
In addition, much of the research that is frequently cited today is over 20 years old. Advances in genetics, anesthetic techniques and research methodology mean that new data are urgently needed. Population diversity is also important because different MC1R variants may have different effects on response to treatment.
Looking to the future, some researchers suggest genetic testing may ultimately aid in anesthesia selection, especially for patients with a history of anesthesia resistance. The long-term goal is personalized pain management that provides maximum safety and comfort.
Red hair may be associated with subtle differences in pain and drug response, but understanding how and when these differences are clinically significant still requires further research.
This article does not contain medical advice and should be used for informational purposes only.
Read more: Why does our hair turn gray as we age and can we stop it?
Article sources
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