People with red hair have an altered sensitivity to certain types of pain due to the presence of a different form of a receptor on pigment cells in the skin.
- The melanocortin receptor acts on molecules that affect the perception of pain.
- In redheaded people, this receptor is inhibited, which automatically raises the pain threshold.
- These receptors are also involved in tanning and explain why redheads tan less.
Red-haired people are less sensitive to pain. American researchers from Massachusetts General Hospital (MGH) suggest that this particularity is caused by the presence of a mutation in the melanocortin-1 receptor (MC1R) present on the pigment cells of the skin, which is involved in the perception of pain. The findings were presented in a scientific paper published April 2 in the journal Science Advances.
The deciphered mechanism
The researchers tested pain thresholds in red-haired mice that possess the mutation on the melanocortin-1 receptor. They found that without this feature, the pain threshold appears higher. This is explained by the pigment cells of the skin, the melanocytes, of the animals which secrete lower levels of a molecule called POMC – for proopiomelanocortin. This molecule plays an important role in pain sensitivity since it maintains a balance between opioid receptors which inhibit pain and melanocortin receptors which improve pain perception. Therefore, low levels of POMC cause more signals to arrive at the opioid receptors, which automatically raises the pain threshold.
“These findings describe the mechanism behind previous evidence suggesting varied pain thresholds as a function of skin pigmentation.explains David Fisher, lead author of the study. Understanding this mechanism provides validation of this prior evidence and valuable recognition for medical staff when caring for patients who may vary in pain sensitivity..” The researchers add that these results make it possible to design new drugs that inhibit the melanocortin receptors involved in the detection of pain.
These receptors also explain tanning
The inability of red-haired people to tan or darken their skin pigment is also attributable to inactive variants of the melanocortin receptor. This receptor is responsible for switching the production of yellow and red melanin pigment to that of brown and black melanin pigment in melanocytes.
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