Check Up: Drexel group finds cause of eczema itch

Tom Avril, Inquirer Staff Writer Posted: Sunday, February 23, 2014, 8:51 AM

Patients with eczema tend to start itching before they see a rash, rather than the other way around, leading some to call it "the itch that rashes."

So what is this invisible agent that causes the itch?

Herbert B. Allen has been scratching his head over that one for years, but recently the Drexel University dermatologist achieved a measure of intellectual relief.

He and a team of colleagues at Drexel's College of Medicine report that the culprit is a slime-like substance called biofilm, produced by Staphylococcus bacteria on the skin.

The biofilm blocks sweat ducts, which in turn activates an immune response that leads to itching and inflammation, the team reported in the journal JAMA Dermatology.

Dermatologists have known for years that staph bacteria were somehow involved in the process, and they have known about the molecular pathways that lead to itching and inflammation.

What is new is the finding that the blocked sweat ducts lead to activation of the inflammatory response, said Allen, chairman of the medical school's dermatology department.

"This is kind of the missing puzzle piece," Allen said.

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Check Up: Drexel group finds cause of eczema itch