100 Interviews

In The Future No One Will Itch: An Interview with Washington University’s Dr. Zhou-Feng Chen

by: Gaby Dunn

Imagine a future where no one would feel a simple itch.

Whether you find it soothing or annoying, itching isn’t usually a topic studied in the medical world or one that healthy people consciously think about. It’s neurological, dermatological and psychological — and now, for the first time, itch is going under the microscope.

I first read about Dr. Zhou-Feng Chen’s research into itching in the July issue of Scientific American. I was fascinated by the idea of studying something so commonplace and yet still so mysterious scientifically. Chen is the director of the first Center for the Study of the Itch, which opened at Washington University in St. Louis last spring.

Dr. Chen first came to Wash U to study pain, and stumbled into studying itch by accident: when a receptor thought to be for pain, ended up being for itch.

It was fate. As a child, Dr. Chen has suffered from debilitating atopic dermatitis. From the time he was six years old to the time he was ten, he itched so much that his mother, every night, tied his hands to his bedpost to prevent him from scratching himself.

Those terrible years stuck with him, and so though Dr. Chen didn’t set out to devote his life to itching, it seems it was one area he just couldn’t scratch.

Gaby: Thank you for calling. I’m so excited to talk to you, ever since I read about you. I’m going to completely nerd out. But first, tell me: Why did there need to be an entire center devoted to studying itching?

Dr. Chen: Thank you. I went to your website last night. I think that you are doing something very interesting.

Okay, so we realized that itch is a huge problem; it’s not just some minor irritations. There are lots and lots of chronic itch sufferers. They just scratch in all kinds of places. There was really nobody taking it seriously. One possibility is that people that suffer chronic itch, they tend to see dermatologists and, in fact, itch is a problem for neuroscientists.

Gaby: In Scientific American, you said that people think that pain and itch go together. But actually, they’re opposites.

Chen: Most people think that they are transmitted through the same pathway. We accidentally found the receptor located in the same area, in the spinal cord, which is important for pain transmission. So we thought it could be very important for pain transmission, but we found that it has nothing to do with the pain. Rather, it turned out to be very interesting for itch transmission.

They actually are quite complex. There are still lots of scientists who think that itch and pain are transmitted the same, go together, transmitted through the same pathway. And there is lots of evidence for that in many, many places. But if you say itch and pain are transmitted together, you can’t really explain why itch and pain are different. Sometimes they even antagonize each other. That doesn’t explain how itch can become pain, because these are two sensations. They are very distinct. So when you itch, clearly you can tell you are itching. You will never mistake an itch as a pain, right? So they are clearly very different.

Gaby: Is it neurological?

Chen: Well, most patients when they itch, they actually will feel it on their skin, so they scratch. That’s why most of the patients, they go to see the dermatologist. But then there are still some portion of patients, they feel itching from inside. So they go to see the neurologist or see other physicians, other type of internal medicine or physicians. So there are clearly different categories of different type of itch. Not all itches reflect on the skin.

Gaby: Like when your throat itches or when the top of your mouth itches? That’s neurological, right?

Chen: Yeah. Actually, the itch is a complex sensation, because not only is there a neurological itch or a skin‑related itch, but then there is also a psychological itch. One of the common phrases we use, “He’s scratching his head,” because he doesn’t know the answer. So when people ask you difficult questions, you don’t know the answer, you’re a little bit embarrassed of that. Then you have to do some behavior to release the kind of stress or pressure, so you scratch your nose, your head, unconsciously. That’s a type of psychological itch.

Gaby: Is there some sort of evolutionary reason for itching?

Chen: Yeah, there’s definitely an evolutionary reason for it. You can imagine at the very beginning when our ancestors, they don’t have clothes to wear so most of their skin is all exposed to the environment. That environment is pretty harsh. There are quite a few fundamental sensations required to protect yourself. One is obviously the pain sensation. You feel injury or you feel something, heat, and some kind of mechanical injuries. So that is a way to make you restore your body, to protect yourself.

So the pain sensation is very primitive and a fundamental, a very important sensation, which protects you. You remove your body from a harmful source.

However, there are lots of types of environmental stimulus, such as something sticking to our skin like an insect biting, a mosquito, those kinds of things. You can’t always restore yourself to protect from those stimuli, because lots of times when it sticks to us, it stings and then it goes with you.

So you have to remove it, remove those kinds of irritating substances sticking to your skin. You may not have realized when a mosquito is sticking to your skin, sucking the blood, those kinds of things. That’s probably the reason that you need another type of sensation, which allows you to remove those kinds of irritating substances to your skin to protect you. So that’s probably where we came up with the itchy sensation.

Gaby: Is there a way to just eliminate itching altogether?

Chen: Actually, that’s quite interesting. I’m glad that you raised this question. Because obviously, we can see that there are some reports of people that have congenital insensitivity to pain stimuli, right? They don’t feel pain. But very interestingly in most cases people don’t mention their itch. So the people don’t mention their itch. Where those people, they are insensitive to pain, they cause a lot of injury or problems because of that.

Gaby: Do those people itch?

Chen: I have paid attention for those kinds of things. There is actually a few reports. I noticed in the report that itch sensation is intact in those patients. That’s actually a pretty strong argument to argue itch and pain are actually different.

When patients feel terrible pain, one thing sometimes their surgeons try to do is cut off the pathway transmitting pain. Oftentimes, they find with those patients, they feel pain relief and they also don’t feel itch. However, I think one possibility is when you perform this surgery, because you may not be very precise, you may also somehow ‑‑ you didn’t realize ‑‑ damage the itch pathway.

When I look at it more, indeed, I found a few case reports when the physician performed the same type of surgery. They tried to treat the pain. Actually, there is one report that says the patients, they don’t feel pain anymore, but the itch is still intact. They still feel itch normally. Those cases, actually, are a much more convincing case to argue itch and pain are transmitted separately.

Gaby: So there is a way to get rid of itching in people forever.

Chen: I think it is possible because this we have achieved a lot in mice, right? In mice, we identified the neural express of these receptors, called the GRPR, gastrin‑releasing peptide receptor. If we kill all these receptors, we remove those receptors by ablation or by killing off the cells specifically. So we can eliminate it; mice don’t feel the itchy sensation anymore. But they still respond normally to a wide variety of painful stimulus.

If the same set of itch neurons exists in humans, you can imagine you can do the same thing. You can treat those people with the powerful itching cure. Remove those itch neurons, and then people will not feel any itch sensation, but their pain pathways should be normal.

Gaby: Are there negative consequences to that?

Chen: I don’t think there’s any negative consequences because nowadays, we have much better living conditions. People live in air conditioning, or you wear coats. Most of the time, you don’t need the itchy sensation. But you do need the pain sensation to protect yourself. But I think the itchy sensation is something that is dispensable.

Of course some people complain. “Why do you want to get rid of the itchy sensation?” Because they say, “I enjoy scratching myself. The scratching gives me a tremendous sense of pleasure.” There are different types of itchy sensation, yeah.

Gaby: People that don’t itch chronically, I imagine, take it for granted. If you have a disease where you itch all the time, then eliminating itch is a big help.

Chen: Most people, they scratch a little bit and they don’t think it is a major problem. Nowadays, the people send me an email. Almost every other day I get an email from patients. They’re all over the world. So you get to know lots of people. You can see they are in all different places. They suffer terrible itching. It’s about to 20 percent of kids, they suffer from atopic dermatitis. People don’t know why they scratch.

Gaby: Let’s say your ear starts itching, what is that from? Is that just a misfire of a neuron?

Chen: Well, the itching sensation is a perception from your brain. So this kind of perception can be generated by different mechanisms. The itching receptor can be very easily activated, probably more easy than other sensations. So it’s just there as you lay very quietly on your bed, and you don’t think about anything. All you think about is your body. So the first sensation coming to your mind may be you feel somewhere you want to scratch. You can activate the itchy sensation simply by thinking about itch, right? It’s almost immediate. Itching is a perception, right? When you talk about a perception, it’s a part in your brain. So if there’s no brain, no itchy sensation. But then there’s a scratching behavior. It’s located in your spinal cord. In terms of perceptions, it’s generated from within your brain to your spinal cord.

Gaby: What are the things that you’re working on now at the center?

Chen: So the major thing is because we identified this first, the itching‑specific receptor. This is something that excited a lot of people. Because before we found this, people never really thought about it and nobody took it really seriously. Now, we’ve shown them that there’s an itch‑specific receptor there, and potentially could be a target to developing some of the drugs, and you can treat some of the chronic itch patients with drugs, with medicines. Then that will help relieve millions of people and improve their quality life, right?

So far, if you think about a histamine, like an antihistamine. There are lots of acute types of itch that’s mediated by the histamine, like a Benadryl. You go to a grocery store, take some Benadryl and then you feel better. So you can see those kinds of medicine really help a lot of people. But the problem is, the majority have a chronic itch. That’s an itch that persists for several months, even for years. I have people writing to me, who say, “I have had a chronic itch for 20 years.” So in those people, antihistamine doesn’t work. Nobody knows what kind of medicine can work. Those are the kinds of patients that really need help.

We try to understand what, whether all itch receptors play an important role in those types of chronic itch. Or can we find a way to develop a medicine to translate our study into a treatment? So that’s a goal for our itch center.

Gaby: What’s the best remedy for a mosquito bite?

Chen: When you have an itch like a mosquito bite, probably, if you like, you can put some Benadryl, those kinds of things, so antihistamines. Most of our antihistamines work for those types of itch and some type of chronic itch people also take antihistamine. Some patients say, “Oh, it looks like it works.” But actually, that’s not because of the anti‑itchy effect. It’s because when you take too many of those kinds of Benadryl, sometimes those other drugs, it causes sedation. The drug makes you falling to sleep. So when you get into sleep, so you may feel less itchy.

Gaby: Do you think that you’ll eventually figure out a way to stop itching in humans forever?

Chen: I think that eventually, yeah, we will be able to figure out a way to stop or make less those kinds of itching. Right now, nobody understands why they itch. Once we know more about how about itch is transmitted in our bodies, we will be in a much better position to stop it. But right now, we are just at the very, very beginning. We have a long, long way to go. We have just started.

We don’t know whether there is an itchy center in the brain or not. I guess that probably there will be some itch center in the brain as well, or itchy‑specific neuron in the brain as well. But right now, we just don’t know yet.

Gaby: It’s a good start.

Chen: There are many, many pain centers in our world, that I am delighted to have an itch center to study the itch mechanism. So it’s an exciting time to do itching research. We have a long way to go, yeah. A long way to go.

—

Gaby Dunn is a writer, journalist, comedian and the founder of 100 Interviews. Her writing has appeared in The Boston Globe, The Huffington Post, The New York Times Magazine and on Salon, The Good Men Project, Thought Catalog, and Jezebel. She subscribes to two science-based magazines. She is not a scientist. Follow her @gabydunn. Photo courtesy of Creative Commons.