Why do we itch?

| Melissa Leavitt

Growing up in the 1970s, Christina Tom refused to wear polyester. But bucking the decade’s distinctive style trend wasn’t a fashion statement. Instead, it was an attempt to relieve the itch from her psoriasis. Polyester clung to her skin, she said, making the itching worse. But even avoiding polyester didn’t bring much improvement.

“Itch became a way of life growing up with psoriasis,” said Tom, who lives in Brooklyn, New York.

She itched every day, and she seemed to itch everywhere.

At 51, Tom said her psoriasis has greatly improved, and the itch has faded. But she still remembers what she describes as the “red hot” sensation of psoriatic itch.

She’s not alone

Research shows that many people with psoriasis — as many as 84 percent of people with extensive psoriasis, according to a November 2000 study published in the British Journal of Dermatology — suffer from itch. The same study found that most patients felt little relief from anti-itch treatment.

Mike Bozyczko was no exception. When his psoriasis was severe, “It itched like crazy,” said the 57-year-old from Poughkeepsie, New York.

“I was itching all day long,” he said.

But scratching didn’t help. When he scratched, his skin would flake and bleed. Still, he kept scratching, unable to break the cycle.

“You knew you were doing damage to yourself, and you couldn’t stop,” Bozyczko said. “It was almost like something you couldn’t help doing.”

Tom also found her itch — and the urge to scratch — to be intense and unlike anything else she’s ever experienced.

“Psoriasis itch is a different type of itch,” she said. “It’s from head to toe, inside coming out. It’s your brain telling you that you have to scratch.”

Scratching beneath the surface of itch

Once overlooked as a symptom of psoriasis, itch is now coming to the forefront of psoriatic disease research and care. Scientists are looking at the different causes of itch in psoriasis and developing new therapies that could change the way doctors treat it.

A big part of this research is identifying the different systems in the body that contribute to psoriatic itch. There’s a reason that psoriatic itch can feel like a message coming from your brain. That’s because the brain, and the entire nervous system, are key players in itch.

But the nervous system isn’t doing it alone. 

“In the body, everything is talking to everything else,” said Dr. Ethan Lerner, a Harvard University dermatologist who studies itch.

And the conversation between the immune system and the nervous system can leave psoriasis patients feeling itchy.

“We’ve known for a long time that psoriasis is an inflammatory disease,” Lerner said.

In people with psoriasis, immune cells and inflammatory proteins are perpetually in attack mode, triggering rapid growth of skin cells, and thus, an inflammatory reaction that shows up as red, flaky plaques on the skin.

But until recently, researchers haven’t paid as much attention to the role of the nervous system in psoriasis. Itch is caused by nerve stimulation, Lerner said. Understanding how
the nervous system contributes to psoriasis inflammation — and how inflammation interacts with the nervous system – could be the key to understanding why itch can be part of the disease.

One explanation may have to do with the pro-inflammatory proteins, or cytokines, involved in psoriasis. Some of these cytokines may activate nerve fibers, said Dr. Gil Yosipovitch, chair of the dermatology
department at Temple University and director of Temple’s Itch Center.

Other sources of itch in psoriasis may be found in components of the nervous system, such as neuropeptides, Yosipovitch said. Neuropeptides are molecules that help neurons communicate with each other. One possible candidate is Nerve Growth Factor, while another is known as Substance P, according to Yosipovitch.

Itching to feel better

If itch is located at the intersection of the immune system and the nervous system, it makes sense that treating it could involve targeting both the inflammatory and the nerve pathways.

Most psoriasis therapies work by modulating the immune system. Because itch often fades when plaques do, treating psoriasis by targeting the immune system could bring about relief from itch. Both Tom and Bozyczko have found clearer skin — and relief from itching — after being on biologics for a while.

Newer biologics may also offer itch relief. One is ixekizumab, a biologic being developed by Eli Lilly that has been shown to effectively treat itch.

Data from a Phase III trial of the drug presented last October at the European Academy of Dermatology and Venereology conference found that patients on ixekizumab reported significantly greater improvement in itch than patients on the placebo. Improvement was seen after one week taking the drug and lasted through three months, according to the data.

Some tried-and-true psoriasis treatments may also deliver rapid relief from itch. According to Lerner, phototherapy can improve itch before it reduces the appearance of psoriasis, and it may even herald greater
improvement to come.

“Improvement in the itch is a sign that their psoriasis is going to get better,” he said.

Scientists are also working on therapies that reduce itch by targeting the nervous system. Drugs that target neuropeptides like Substance P and Nerve Growth Factor are in development, Yosipovitch said. They
block these pathways by inhibiting their receptors, which communicate with the neuropeptides.

For example, a topical medication made by Creabilis, called CT327, targeting a receptor for Nerve Growth Factor called Tropomyosin receptor kinase A, or TrKA, is in clinical trials.

Results from a Phase II trial of the ointment for psoriasis, which were published in the journal Acta-Dermato Venereologica in May 2015, found that for up to 62 percent of patients, it improved itch by 50 percent after two months of use. But it was less effective at improving the appearance of psoriasis, researchers reported. Yosipovitch, who was involved in the clinical trial, noted that CT327 may be especially useful for treating more localized itch. 

Patients should work with their doctors to find the best remedy for their itch. In addition, many patients find that certain fabrics and products that soothe the skin can also help ease itch.

Long past her struggles with 1970s polyester, Tom now tries to wear natural fibers such as cotton or silk against her skin. She’s more comfortable in breathable fabrics, she said. And Bozyczko found that moisturizer helps his itch.

“I found that the more moisture I put on my skin, the more relief I got from itching,” he said.

He uses Aquaphor, he said, and has also heard from friends with psoriasis that coconut oil can be good itch relief.

Yosipovitch also recommends moisturizer to his patients. Dry skin, as is seen in psoriasis, damages the barrier of the skin, which can result in itch. “Any damage to the barrier of the skin triggers the nerves to be activated,” Yosipovitch said. “Moisturizers can improve the barrier."

He also suggested that people with itch look for cleansers and other products with a low pH or level of acidity.

A tough itch to scratch

But what about the thing that seems like it would offer the most rapid relief — scratching? Bozyczko found that scratching sometimes made his psoriasis worse.

The reason, according to Yosipovitch, goes back to the importance of maintaining a healthy skin barrier.

When patients scratch, they can damage their skin barrier. Any damage of the skin can lead to what’s known as a Koebner effect, Yosipovitch said, which is when skin injury triggers psoriasis.

Stress and anxiety can lead to itch, too, so stress-relief strategies could also bring about itch relief, said Yosipovitch.

For Tom, the trick to fighting itch — and the urge to scratch — was taking a deep breath. “It’s you against that itch,” she said.

Overcoming it was a battle, she said, one she needed to wage with her body and mind.

“I took a deep breath to calm myself. And I clenched my fist,” she said. “I would get up, walk away and calm myself.”

Today, patients are getting more help in waging what can feel like a never-ending battle against itch. Doctors, researchers and drug companies are finally realizing how important getting rid of itch is to patients, Yosipovitch said.

Within the next five years, he noted, we could see dramatic advances in our understanding of what causes — and what can improve — itch.

“We’re getting closer to understanding the unmet needs of the patient,” Yosipovitch said. “It’s an exciting time.”

Why does your psoriasis itch? Ask a mouse.

Sam T. Hwang, M.D., Ph.D., chair and professor of dermatology at the University of California, Davis School of Medicine, is conducting a study involving mice that analyzes the parts of the brain involved in psoriatic itch. The study is being funded through a $75,000 National Psoriasis Foundation Discovery Grant, awarded in 2015, when Hwang was a faculty member at the Medical College of Wisconsin.

After inducing a psoriasis-like disease in mice — one that causes mice to itch — Hwang and his team perform an advanced type of brain scan called a functional-connectivity MRI. The scan, which requires specially designed equipment small enough to work on a mouse brain, allows researchers to see what happens in the brain when the mice start to itch.

The mice start scratching as soon as 24 hours after the induction of psoriasis, Hwang said. But this is days before inflammation starts to affect the skin and the visible signs of psoriasis appear, making it the perfect time to study how the nervous system contributes to itch.

The study is ongoing. The next step will be to induce psoriasis in mice in a different way — one that doesn’t cause the mice to itch as much — and see if the brain reacts differently.

“What we’d like to see is if the difference in the level of itching is reflected in the MRI. If it is, it tells us that inflammation by itself doesn’t cause these changes. There have to be other pathways that are activated in order to get these brain changes,” Hwang said.

But even before then, Hwang and his team are learning new information about what causes itch, which could lead to new ideas for how to treat it.

“Already, our research suggests that the itching pathways are different than the pathways that induce inflammation in psoriasis,” he said. “One implication is if you had effective drugs that could target the itch pathways, then you could make patients a lot more comfortable, even if you can’t right away treat their psoriasis and make their inflammation go down.”


Driving discovery, creating community

For more than 50 years, we’ve been driving efforts to cure psoriatic disease and improve the lives of those affected. But there’s still plenty to do! Learn how you can help our advocacy team shape the laws and policies that affect people with psoriasis and psoriatic arthritis – in your state and across the country. Help us raise funds to support research by joining Team NPF, where you can walk, run, cycle, play bingo or create your own fundraising event. If you or someone you love needs free, personalized support for living a healthier life with psoriatic disease, contact our Patient Navigation Center. And keep the National Psoriasis Foundation going strong by making a donation today. Together, we will find a cure.

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