Redheads "more susceptible to pain" People with red hair are more susceptible to pain and require more anaesthesia than those with other hair colouring, according to US researchers.
Anaesthesiologists at the University of Louisville's Outcomes Research Institute, in Kentucky, say the findings have implications for redheads who require surgery and provide a better understanding of how anaesthesia works in humans.
Dr Edwin Liem and colleagues found that redheads need about 20 per cent more anaesthesia than people with other hair colours and speculate that this may be due to genetics. They say that variations in the melanocortin 1 receptor, which is associated with red hair, in certain cells may be to blame.
Dr Liem explains that the dysfunction of this receptor triggers a feedback mechanism that increases the release of the hormone that stimulates these cells.
The same hormone also stimulates a related brain receptor that increases pain sensitivity, he says.
The researchers came to their conclusions after looking at healthy Caucasian women aged 19 to 40 who either had naturally red hair or dark hair.
The women were given the commonly used inhaled anaesthetic desflurane and their physical responses were monitored.
"Red hair is the first visible human trait or phenotype that is linked to anaesthetic requirement," according to Dr Liem.
"In a nutshell, redheads are likely to experience more pain from a given stimulus and therefore require more anaesthesia to alleviate that pain," he says.
And Dr Liem believes that the study could have a significant influence for further research into pain tolerance.
"Since red hair can be traced to particular mutations in the melanocortin 1 receptor, we now have the opportunity to evaluate central nervous system pathways that may influence or mediate anaesthetic requirement.
"Investigating the role of melanocortin system in the central nervous system is thus likely to help us understand fundamental questions such as which systems in the brain produce unconsciousness and which modulate pain perception," he added.