Blocking interleukin 33 (IL-33)  may put the brakes on the uncontrollable itch caused by poison ivy, poison sumac, poison oak and even mango trees, according to a mouse study conducted by scientists at Duke Health in Durham, NC, and Zhejiang Chinese Medical University in China.

The research appears in the Nov. 7 Proceedings of the National Academy of Sciences.

They hope their model could lead to potential treatments for people who are allergic to poison ivy -- an estimated 80 percent of the population.

Some symptoms of poison ivy can be alleviated with antihistamines and steroids. But in recent years, scientists have determined that the most severe itching doesn’t go away with antihistamines, because it arises from a different source, explains senior author Sven-Eric Jordt, Ph.D., an associate professor of anesthesiology at Duke, in a news release.

IL-33 is elevated in people who have eczema and psoriasis, Jordt says. The protein is known for inducing inflammation, but these new experiments show it also acts directly on the nerve fibers in the skin, exciting them and telling the brain that the skin is severely itchy.

The researchers used an antibody to block IL-33 and found that it not only reduced inflammation, but also cut down scratching in mice with poison ivy rashes. An antibody that counteracts human IL-33 is currently being evaluated in humans through a Phase 1 clinical trial to determine its safety and potential side effects.

In an additional approach tested in the mouse experiments, the researchers also found they could also alleviate itch by blocking a receptor for IL-33, called ST2.

“There could be translational significance here,” Jordt says. “So our next step will be to look at human skin to see if we see the same activity and the same pathways. We will also look at anti-inflammatory drugs that are already approved to see if they have the potential to alleviate itch.”

PHOTO CAPTION/CREDIT: A fluorescence microscope image shows the skin of a healthy mouse (left) and skin from a mouse with a poison ivy rash (right). Interleukin-33, shown in green stain, is a protein that acts directly on the nerves, telling the brain the skin is extremely itchy. Sven-Eric Jordt/Duke Health