Short Wave - Itchy? Here's why

Episode Date: September 25, 2023

Ever had an itch you can't scratch? It can be maddening. And even though itch has a purpose — it's one of our bodies' alert systems — it can also go very wrong. Dermatologist Dr. Shawn Kwatra talks to host Regina G. Barber about the science of why and how we get itchy, the mysteries behind chronic itch and how his own experience with eczema, hives and seasonal allergies helps him connect with his patients.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Before we begin, heads up that next week is NPR's Climate Week, where we'll spend seven days focused on innovators working to build a better world for the next generation and the one after that. On Monday's episode of Shortwave, we'll hear how a robot is cleaning up toxic seaweed. And you can also check out more stories of human ambition fighting very human problems at npr.org slash climate week for a spotlight on solutions. You're listening to Shortwave. from NPR. Dr. Sean Quatra is a dermatologist, and he's drawn to one particular part of the dermatology field.

Itch. I myself have suffered from chronic itch my whole life, and I have eczema. I also have hives, a urticaria. I also have asthma and seasonal allergies. So I'm walking around like a very allergic little fellow, and I've grown into an allergic adult as well, but I think it's been able to give me more empathy in treating patients.

Itch. It's literally defined as a sensation that's accompanied by an irresistible desire to scratch. Our research is trying to find out why people itch and how can we treat it? And most everyone has felt itchy. Usually it's just annoying or inconvenient. Or if you're like me, you had chickenpox as a small child and it was maddening, but only for a couple days. But sometimes, Sean says itchiness can be a big problem.

Unfortunately, many itch patients are lost right now. Chronic pain has a lot of appreciation about the effect on quality life. But I would argue the effect of chronic itch on quality life is just as severe, if not greater. And there's very limited therapeutics. And that's because compared to pain, there's just not as much research into how and why we get itchy. It's actually one of the last frontiers and our entire specialty. So there's a lot of unanswered questions. And 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. And there's so many different causes and so many different therapeutics that no one truly knows what to do. Sean is trying to change that as the director of the Johns Hopkins Hitch Center. Over the years, he's seen a lot of patients who've experienced chronic itch. So a few years ago, he took what he learned and co-wrote a two-part article in the Journal of the American Academy of Dermatology. And we suggested a workup for the patient who has chronic itch when they come in. We want to make sure there's no underlying liver or kidney disease, make sure we're checking their blood counts.

Also, just making sure there's no other serious symptoms, be in underlying malignancy or anything like that. Think a standardized checklist a doctor could use to try and figure out what's causing the itchiness. So that's been one of the biggest joys for me is being able to take those insights that we have at the bedside, go back to the laboratory or through a clinical trial and test hypothesis. And then, you know, we can make an impact on therapy because there's many patients that are suffering, I think, because there's a lack of standard of care because that lack of understanding. Today on the show, we dive as deep as we can into researchers' understanding of itch. We get into the science of why it happens and why some people just can't stop.

I'm Regina Barber, and you're listening to Shortwave, the science podcast from NPR. Okay, Sean, let's just get to the bottom of this. Why do our bodies get itchy? So I think the way to think about it is with evolution, there's usually a reason for certain things and for for chronic itch, think about olden times, folks would have this itch and it would be a signal that there may be danger, there may be a poisonous plant, there may be a tiny bug. And so that signal is that there is something foreign here that might be dangerous and that we need to take action upon and remove it via the scratching reflex. And if you think about folks and all of our

ancestors who are living outside and encountering all sorts of bugs and poisonous plants and animals and all these different things, having such a reflex is such an advantage because you can prevent all sorts of terrible things from happening. So it's basically your body's warning signal that has gone haywire in chronic itch, you know, patients. Can you talk a little bit more about itch and its relation to the immune system? Absolutely. So the immune system plays a very important role in itch biology because they're one of things that can stimulate and irritate these nerves that are transmitting the itch message. So, for example, if a person has eczema, then basically they have a little bit of a barrier issue in their skin, which I have as well, and that makes your

skin more likely to get irritated by even creams or pollutants or things in your environment. And when that happens, you have many of these immune cells that are warrens. signals in your body that then release substances that can trigger these nerves. So the immune system plays a really important role in many forms of itch because they are what stimulates these nerves. And if you can knock down that stimulation of nerves, in many cases, you can cure itch. So how is itchiness different from pain or feeling like pressure? Like what's the wiring? How is it different for itch? Yeah, so basically they're nerve fibers from your skin that go towards your spinal cord and brain. Those nerve fibers that transmit

itch also transmit pain. They also transmit temperature or vibration sensations. But in 2007, there was actually a really landmark paper that showed that there's a very specific pathway within these nerves for itch. And what we're learning more and more is that there are very unique aspects of these nerves and certain molecules that are specifically targeting the it, which has led to a lot of breakthroughs. So, like, how does scratching help relieve itching? Scratching interrupts, at least temporarily, that sensation of itch. And what it also does is the mild pain sensation that's induced by scratching causes the

release of serotonin, which is actually your body's natural pain reliever in a way. Oh, okay. And so the serotonin is able to help block the itch. But then the brain continues to send more signals of itch. You then scratch more, which triggers more pain. And then you get more serotonin. And then unfortunately, you end up being stuck in this intractable, itch scratch cycle. But that pain release and that serotonin release is initially what is responsible for that temporary relief that people can experience.

Wow. So is there research on why we feel itchy? when we see somebody else scratching. So there are mirror neurons in the brain. And so if you watch a video of someone itchy, then you're going to also oftentimes start itching. But if you think about it from an evolutionary perspective, it kind of makes sense that if you're outdoors, say,

and you see someone else who's itching, then that's an alert. There is something potentially hazardous in our environment. It may be on you too. So you should start scratching. And it's just so fascinating that's been conserved. Makes me think of lice. Like, I have a child and, like, you know there's the time when the kids, like, the lice phase, you know, and like everyone's itching. And you're like, oh, God, I hope we don't have lice.

And then when you think about lice, you can't stop. Can't get out of your mind. You can't stop thinking about it's everywhere. It's funny as docs, too. Sometimes when we see folks who have some infectious diseases like scabies, we then, you know, can't stop itching. So it affects us too. It actually hits on something that's very interesting about itch.

There's actually a big placebo effect in itch because the central nervous system, the brain, mirror neurons, like all of these factors are so important. And the nerves are so linked into this process that actually the placebo effect is pretty substantial in itch patients. Yeah. No, I can totally see it. Like as we're talking, I'm like itching. You know, it's funny because what we treat patients with is antihistamines. But antihistamines only work usually for disorders like hives because they have high histamine. 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.

but when you give the anihistamines, if they're sedating, they'll make you tired, or if they're non-cedating, there is some of that placebo effect. That's so fascinating. So placebo effect may bring you down a point or two, but imagine if you have very severe itch, near a 10 out of 10. Going down to a 9 or 8 is not really going to be significant. So if the anihistamine doesn't work, what do you do? So many times now, I'm not even prescribing them first line because we're learning a little bit

more about anihistamines. Even non-cedating anihistamines have been associated some studies with dementia. Wow. And cognitive effects. So I'm actually pretty careful with it. The first thing I do is I try to figure out when I'm diagnosing a patient, is there relatively more involvement of the immune system or the neural system? Because itch is neuroimmune in nature. So things I do is I order a blood count, and I'll look at the percentage of bloodiestinophils or another more. marker called IGE, fancy names, but they're just biomarkers. And if they're high, that's a really good indication that your immune system is causing that itch. So we're learning so much right now. And there's so much of being a diagnostician in treating these patients to really get at the

underlying root cause. Wow. Okay. So, I mean, that brings us to, like, what's the most recent kind of big discovery in your field or like what do you want to find out in your field either one i think the movement is clear it's towards precision medicine what that means is inhumans taking all sorts of itch patients together what are the similarities but what are also the differences so you know trying to figure out exactly what's going on with these unique subgroups of patients so that's really exciting for us and being able to see a patient in my clinic and know that they're having you know, kind of intractable itch, but then be able to, in the laboratory, go back and try to find out exactly what's going on in them has been very rewarding.

And I'm glad you, like, share with your patients, like, this happens to me to, you know, I'm not immune to these things because I'm the doctor, you know. No, I think it helps reach folks because sometimes you don't know if people actually appreciate what you're going through. Right. And as a doctor, being able to know, you know, how bad that feeling can be and that urge to to get rid of the itch. It's so important and powerful, and it can impact sleep especially. So itch and sleep are very intimately linked. And that's why many chronic itch patients, they get

terrible sleep, and then they have terrible work performance. Their relationships suffer. I mean, when you don't sleep a lot, I'm sure you get very tired and cranky. I get so cranky when I don't sleep. And this is actually the de facto working level that many folks are dealing with who have chronic itch. It's very, very sad. This research is actually very personal to me, but I think it's been able to give me more empathy in treating patients. This has been really enlightening for me and a little bit of itchy, but thank you so much for talking to us. Thank you so much for having me. I really appreciate being on. If you've been enjoying this episode, give us a follow, so you'll be alerted each time we publish a new episode. And if you have any story ideas,

send them our way. Our email is Shortwave at NPR.org. This episode was produced by Burley McCoy, edited by our managing producer Rebecca Ramirez and fact-checked by Nile Oza. The audio engineer was Gilly Moon. Beth Donovan is our senior director and Anya Grunman is our senior vice president of programming. I'm Regina Barber. Thank you for listening to Shorewave from NPR.