Scientists Discover Why Sunburn Hurts

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Scientists at King’s College London have pinpointed the exact molecule that causes the stinging, tender pain of sunburn. Targeting the molecule could help pave the way to more effective pain treatments, not only for sunburn but also for other inflammatory conditions like arthritis.

The culprit is a protein called CXCL5, which recruits inflammatory immune cells to damaged tissue and triggers the familiar sting of too much time spent at the beach.

To identify the protein, the scientists asked healthy human volunteers to expose small patches of their skin to UVB radiation, the type of radiation from the sun that is most responsible for sunburn. The exposed patches started becoming tender over the ensuing few hours, peaking in pain one to two days later — which is when the team biopsied the affected skin to look for proteins associated with the pain.

Several of these pain mediators, including CXCL5, were overexpressed. So scientists turned to rats for confirmation. They found that CXCL5 was overexpressed in sunburned skin in both humans and rats, and that when rats were given an antibody that targeted and neutralized CXCL5, their sensitivity to pain was significantly reduced.

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The discovery may amount to more than just fodder for interesting lunchtime conversation. It may help scientists better understand how pain works, which could further lead to the development of better treatments — not only for the throbbing pain of sunburn, which is notoriously hard to ease, but also for other aching conditions that involve inflammation.

“We hope that we have identified a potential target which can be utilised to understand more about pain in other inflammatory conditions like arthritis and cystitis,” study leader Stephen McMahon said in a statement. “I’m excited about where these findings could take us in terms of eventually developing a new type of analgesic for people who suffer from chronic pain.”

It’s no excuse for forgoing sunscreen at the beach this summer, but it’s nice to know that relief from the sting of sunburn is possible.

McMahon’s study was published in the journal Science Translational Medicine and was funded by the Wellcome Trust and the U.K.’s Biotechnology and Biological Sciences Research Council.

Tara Thean is a TIME contributor. Find her on Twitter at @TaraThean. You can also continue the discussion on TIME‘s Facebook page and on Twitter at @TIME.

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