Red hair doesn’t explain differences in pain

The Tweet: “Redheads don’t feel pain like everyone else does. They are less sensitive to electrically induced pain, but more sensitive to thermal pain.”

Sensitivity to pain has been linked to the gene responsible for red hair colour and pale skin in humans. Melanocortin-1 receptor (MC1R) genes determine the level of the brown skin pigment melanin. Red haired people have a variation of MC1R that produces less of this pigment, resulting in a lighter skin tone. But whether red haired people are more or less sensitive to pain, heat, electrical stimuli and analgesics has been argued either way.

Liem et al. found that red haired women were more sensitive to thermal pain, and more resistant to the effects of the analgesic lidocaine – commonly used in minor surgery to relieve pain from skin inflammations. “Anesthetic requirement in redheads is exaggerated, suggesting that redheads may be especially sensitive to pain,” observed the researchers from the University of Louisville in 2005. This led the researchers to conclude that mutations in the MC1R gene are responsible for pain sensitivity, and matched their previous findings.

Research conducted in 2011 looked at pain tolerance in red haired and blond or dark haired women by applying pressure, heat and a pain-increasing cream to their arms. The cream contained capsaicin – a component of chilli peppers – which produces a sensation of burning when applied to the skin. There was little difference between the two groups for sensitivity to pressure and heat, but for red haired women the cream had less of an effect suggesting they were in fact more tolerant to this type of pain.

However, analgesic efficacy has been linked to a whole host of genes, not just MC1R genes; findings are frequently contradictory and the difficulty creating adequately sized and controlled studies means its not possible to say that red haired people process pain differently to others. In our bodies pain transducers, neuronal activity, illness and our immune system all affect our sensitivity to pain and controlling for these in scientific studies is very difficult. A review of the current literature on red hair and pain sensitivity by Audun Stubhaug in the Scandinavian Journal of Pain suggests that because there are so many different types of pain and other factors that can change our sensitivity it’s unlikely one gene alone will have a significant effect.

Image credit: savagecabage (Flickr)
This post was first published on The Untweetable Truth (6/11/2014)

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