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New research from the USA indicates that allergans in the environment are often to blame for acute itching in people with eczema.

Making matters worse, this kind of itching may not respond to antihistamines, because the itch signals are carried to the brain along a previously unrecognized pathway which current drugs don’t target.

The latest research from Washington University School of Medicine in St. Louis, published in the journal Cell, points to a new potential strategy to help eczema patients cope with these episodes of acute, severe itch that make their lives so miserable.

Principal investigator Brian S. Kim, MD, a dermatologist and Associate Professor of Medicine said, ‘Years ago, we used to think that itch and pain were carried along the same subway lines in the nerves to the brain, but it turned out they weren’t, and these new findings show there’s another pathway entirely that’s causing these episodes of acute itching in eczema patients.

‘The itch can be maddening. Patients may rate their chronic itch at around a 5 on a scale of 10, but that goes up to 10 during acute itch flares,’ he said.

‘Now that we know those acute flares are being transmitted in an entirely different way, we can target that pathway, and maybe we can help those patients.’

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Why antihistamines don’t work

Researchers explained that the typical pathway for itching in eczema patients involves cells in the skin that are activated and then release histamine, which can be inhibited with antihistamine drugs.

But with this acute itching, a different type of cell in the bloodstream transmits itch signals to the nerves. Those cells produce too much of another non-histamine substance that triggers itch, so antihistamines don’t work in response.

‘We’ve connected acute itching in eczema to allergic reactions transmitted by an entirely different population of cells,’ said Associate Professor Kim, who is also the co-director of the Center for the Study of Itch & Sensory Disorders.

‘In patients who experience episodes of acute itching, their bodies react in the same way as in people with acute allergy,’ he said.

‘If we can block this pathway with drugs, it might represent a strategy for treating not only itch but other problems, including perhaps hay fever and asthma.’

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The role of Immunoglobulin

Several clinical studies in recent years have tested a strategy that involves blocking Immunoglobulin E (IgE), a substance produced by the immune system in response to allergens.

Patients with allergies produce IgE, causing allergic reactions, but its role in itch has been unclear. Environmental allergans seem to be the key.

Associate Professor Kim hypothesised, ‘Say a patient with eczema goes to Grandma’s house, where there’s a cat, and that person’s itching just goes crazy. It’s likely cat dander is activating IgE, and IgE is activating itch.’

This theory has been supported by mouse studies.

For itchy humans, the discovery that acute itching in eczema is linked to exposure to allergens may help them avoid things that make them itch intensely, including animals, dust, mold or certain foods.

It also offers drug companies new targets for treating itch in eczema patients, including proteins and molecules which Associate Professor Kim’s team has identified along this newly identified neuro-immune pathway.