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Do People with Red Hair Require More Anaesthesia?

Girl with long red hair with an anesthesia mask. Text above the girl saying "Myth or Fact: Do people with red hair require more anaesthesia"

Written by Selin Eda Sagnak
Illustrated by
Christine Lancion

Most of us have become well acquainted with the term “anaesthetics”- whether it’s from personal experience, anecdotes from friends, or portrayal on TV. Even though its use has become commonplace, there are many mysteries surrounding anaesthesia waiting to be explored.

Have you ever heard that red-haired individuals require more anaesthesia? While it’s a common hearsay, more research is needed to come to a definite answer. So far, there have been studies on this phenomenon that produced contradicting results. A study led by Edwin B. Liem found that people with red hair require 19% more anaesthesia1, but P. S. Myles and colleagues suggest that in actuality, there is no correlation between hair color and anaesthesia requirements.2 Both experiments recognize that people with red hair can have a mutation in their melanocortin-1 receptor gene (MC1R).1,2 Anaesthesia decreases feelings of pain, and if red-haired people need higher doses, we can infer that MC1R mutations dampen the ability of anaesthesia to obscure pain. Currently, its not known whether MC1R lessens pain detection, increases pain detection or has no relationship to pain detection.3 All 3 of these possibilities have been observed in experiments using different types of stimulation, such as electrical and thermal.

Up close DNA illustration of red hair strands with label under "MC1R gene"

You might be wondering, why did Liem and Myles get such different results? Well, one answer to this question might lie in their methodology. Liem only recruited Caucasian women   during the first ten days of their menstruation cycle for the study. Anyone who had “chemical hair treatment, […], any history of chronic pain problems, […] recreational drug usage, and medication usage other than oral contraceptives” was not allowed to participate.1 Myles’s study included participants from both sexes, three smoking statuses (non-smoker, smoker, ex-smoker), and three alcohol usage status (non-drinker, social, heavy). Participants were only excluded in the cases of “not receiv[ing] an inhalational general anaesthetic, […], were being treated with a major tranquilliser or lithium, or had a neurological condition”.2 Taking these factors into consideration, it seems that Liem’s study used a restricted group of participants, resulting in data set that may not represent red-headed people overall. Myles’s study had a larger, more diverse group of participants. While it may seem that Myles collected more reliable results, it must be kept in mind that an increase in variation among the traits of the participants introduces new factors that may individually influence the results obtained. 

So how do we know if red-haired people actually need higher doses of anaesthesia? Do genes causing red hair color have an effect on anaesthetic requirements? Or is this merely a myth, and there is no correlation between the two?

Unfortunately, despite other studies having been conducted on this topic, the scientific community is divided. Anecdotes from medical personnel that describe having to provide red haired individuals with more anaesthetic1 drives this research forward. Scientists, doctors, and red-haired people everywhere still want to know if this is all a coincidence, or if there is a secret connection between red hair colour and anaesthesia requirements. 


  1. Liem EB, Lin CM, Suleman MI, Doufas AG, Gregg RG, Veauthier JM, Loyd G, Sessler DI. Anesthetic Requirement is Increased in Redheads. Anesthesiology. 2006; 101(2): 279-283. doi: 10.1097/00000542-200408000-00006
  2. Myles PS, Buchanan FF, Bain CR. The Effect of Hair Colour on Anaesthetic Requirements and Recovery Time after Surgery. Anaesthesia and Intensive Care. 2012;40(4):683–689. doi:10.1177/0310057X1204000415
  3. Nunez K. Is Hair Color Related to the Effectiveness of Anesthesia? healthline. 2022 Apr 19.