Diagnosing the cause of chronic itch isn't easy, but one man wants to change that

Ever had an itch you can't scratch? Maybe it's out of reach, or your hands are full, or you don't want to damage your skin. It can be deeply frustrating. And even though the itch response, or what scientists refer to simply as "itch," has a purpose — it's one of our bodies' alert systems — it can also go very wrong.

Researchers are trying to figure out what might be going on – and how to help people.

The importance of a regular itch

Itch is evolution's way of drawing our attention to something on our skin that needs removing, says dermatologist Dr. Shawn Kwatra, a leading itch researcher. This could be a stinging bug, a nesting parasite or an irritating plant (poison ivy, anyone?!). All these things urge us to scratch, which generally removes the threat and soothes the itch.

"We know that itch can activate sensory neurons and the signal will be transmitted to the brain. When we scratch the skin, somehow other neural circuits will be activated. And these neural circuits will suppress the itch circuits and alleviate the itch sensation," says Qin Liu, a neuroscientist at the Washington University School of Medicine in St. Louis.

Because the itch sensation has separate neural circuitry from temperature, pressure and pain, applying pressure or ice or scratching can relieve an itch. They're effective neural distractions.

What's the immune system got to do with it?

Oftentimes, when someone experiences hives or an insect bite, histamine is involved, a chemical released by our immune system that can contribute to itchiness. So relieving that itch only requires antihistamine medication.

"But most other forms of itch, like atopic dermatitis, eczema, other conditions, they don't actually have a pathway for histamine as the itch mediator," says Kwatra.

Because of this, antihistamines won't work.

If the cause of the itch isn't obvious, the first thing Kwatra does for his patients is order blood test to determine if the immune system is involved.

"The immune system plays a very important role in itch biology, because [it's] one of the things that can stimulate and irritate these nerves that are transmitting the itch message," he says. "If you can knock down that stimulation of nerves, in many cases you can cure itch."

But sometimes, the itch just keeps coming back.

When itchiness goes haywire and just won't stop

Kwatra studies the world of chronic itchiness. For some people, the itch sensation doesn't go away or flares up when there is no environmental danger. Kwatra sees a wide array of patients, whose itchiness is caused by anything from eczema to hives.

Whatever the cause, treatment options can be unsatisfying. That's because, compared to other chronic conditions like pain, not as much research exists on how and why we get itchy.

"Unfortunately, many itch patients are lost right now. Chronic pain has a lot of appreciation about the effect on quality of life, but I would argue the affect of chronic itch on quality of life is just as severe, if not greater. And there's very limited therapeutics," Kwatra says. Liu agrees.

Kwatra knows personally all about itch.

"I myself have suffered from chronic itch my whole life. I have eczema. I also have hives, or urticaria. I also have asthma and seasonal allergies," says Kwatra.

But for Kwatra, his chronic itch is a powerful tool for speaking with patients. With them, he says he's able to offer more empathy toward his patients, who in turn feel their experiences are better understood.

Creating a game plan to unravel an itchy mystery

But for some people Kwatra treats, there are not clear cut answers. "When patients come in with itch and it's not a clear cut cause, we still don't have a standard of care that everyone agrees upon," he says. "And there's so many different causes and so many different therapeutics that no one truly knows what to do."

Kwatra is trying to change that.

In 2021, he co-authored a diagnostic workup for clinicians in The Journal of the American Academy of Dermatology. It outlines a systematic approach clinicians can follow to diagnose a patient with unexplained itch.

That approach includes screening for a variety of potential causes and takes into consideration several risk factors that are reason for "heightened concern" among clinicians. Some of those factors include: age, as itch is very prevalent in elder populations; race, since itch patients are more likely to be African American or Asian; gender, as women are more likely to experience worse itch sensations.

Kwatra also carefully notes patients with a history of liver or kidney disease. In people with liver disease, the increase in bile and bile acid in the blood can stimulate and trigger the itch response.

"Similarly in kidney disease, the common thread is you get a buildup of many toxins in your body and they can stimulate this itch response," says Kwatra. He adds that genetics and the immune system can also play a role in chronic itch.

In any case, Kwatra says that if you've had an unexplained itch for more the six weeks, it's considered chronic, and it's a good idea to get a doctor's opinion about it.

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This episode was produced by Berly McCoy edited by Rebecca Ramirez and Carmel Wroth. It was fact checked by Anil Oza. The audio engineer was Gilly Moon.