- People with red hair make up a small part of the world's population
- A factor that sets them apart from the rest of people is a different pain threshold
- A new study tested the receptors in redheads and red-haired mice that enable the feeling of pain
Natural red-haired individuals are rare, making up only 2% of the world’s population. With their rare biology, they may be identified by their bright auburn locks and freckled skin.
However, with their uniqueness come uncommon health consequences, like having different pain thresholds than people with different genetics.
'Elevated basal pain threshold'
A study, led by investigators from the Massachusetts General Hospital (MGH) have been exploring the gene mutation in the melanocortin 1 receptor (MC1R) which produces the substance that gives hair, skin and eyes their colour. The study identified that this mutation may be linked to the way pain is felt by red-haired individuals.
According to research published in Science Advances, individuals and mice with natural red hair have an "elevated basal pain threshold and an increased sensitivity to opioid analgesics".
This means that individuals in this group are typically more sensitive to pain and more resistant to pain relief medication. In the study, researchers tested nociceptors, which are receptors that enable the feeling of pain.
To help understand the projected theory behind the different pain thresholds in red-haired individuals, the investigators also studied a strain of red-haired mice that lack the MC1R and display a higher pain threshold.
Evidence revealed that "the loss of the MC1R function in red-haired mice caused the animals' melanocytes to secrete lower levels of a molecule called proopiomelanocortin (POMC)".
It has been reported that POMC "cuts into" different hormones, including one that sensitises to pain and one that blocks pain. The results indicate that the presence of these hormones maintains a balance between the opioid receptors that inhibit pain and melanocortin-4 receptors that enhance the perception of pain.
According to the evidence, having both hormones at low levels in red-haired mice would cancel each other out.
The body is, however, able to produce additional non-melanocyte-related factors that could activate the opioid receptors involved in blocking pain. Consequently, the study found that lower levels of melanocyte-related hormones may elevate the threshold for pain.
Reactions to different kinds of pain
But what's the evidence from an actual red-haired person?
A former Health24 writer tells us it's true: “I know this is true because I’m able to handle tattoo needles without really feeling too much pain.
"I've also noticed that, while other people freak out, I'm not really affected that much by a bee sting," she adds.
New pain-modulating strategies
One of the research fellows in Dermatology at MGH emphasised that with their continuing investigation into the topic, they aim to explain how "additional skin-derived signals regulate pain and opioid signalling".
"Understanding these pathways in depth may lead to the identification of novel pain-modulating strategies."