New research by Harvard Medical School scientists shows that a common skin bacterium called Staphylococcus aureus causes itch by instigating a molecular chain reaction that culminates in the urge to scratch.
“We’ve identified an entirely novel mechanism behind itch — the bacterium Staphylococcus aureus, which is found on almost every patient with the chronic condition atopic dermatitis,” said Dr. Isaac Chiu, a researcher with the Blavatnik Institute at Harvard Medical School.
“We show that itch can be caused by the microbe itself.”
“Itch can be quite debilitating in patients who suffer from chronic skin conditions,” added Dr. Liwen Deng, also from the Blavatnik Institute at Harvard Medical School.
“Many of these patients carry on their skin the very microbe we’ve now shown for the first time can induce itch.”
In their research, Dr. Chiu, Dr. Deng and their colleagues exposed the skin of lab mice to Staphylococcus aureus.
The animals developed intensifying itch over several days, and the repeated scratching caused worsening skin damage that spread beyond the original site of exposure.
Moreover, mice exposed to Staphylococcus aureus became hypersensitive to innocuous stimuli that would not typically cause itch.
The exposed mice were more likely than unexposed mice to develop abnormal itching in response to a light touch.
This hyperactive response, a condition called alloknesis, is common in patients with chronic conditions of the skin characterized by persistent itch.
But it can also happen in people without any underlying conditions — think of that scratchy feeling you might get from a wool sweater.
To determine how the bacterium triggered itch, the researchers tested multiple modified versions of Staphylococcus aureus that were engineered to lack specific pieces of the bug’s molecular makeup.
They focused on 10 enzymes known to be released by this microbe upon skin contact.
One after another, they eliminated nine suspects —…
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