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Interviewer: Bacterial or viral infections, such as COVID-19, head trauma, and some neurological conditions can alter a person's sense of smell. The condition is called parosmia. And for some, it's an inconvenience, but for others, it can get so bad it could impact their physical and emotional health and quality of life.

Dr. Kristine Smith is a rhinologist, which is a nose and sinus expert, at University of Utah Health. And she's going to help us understand what parosmia is, what treatments work, which ones to avoid, and lifestyle changes you can make to help you get through the condition until things start smelling better again.

Dr. Smith, let's start out with what is parosmia?

Dr. Smith: Parosmia really describes an altered sense of smell where people will smell an odorant or an aroma out in the world, and the signal that that will send to their brain, AKA what they'll actually smell it as, comes out wrong.

And the really common descriptions that we get for that are, "I'm trying to cook in my kitchen and everything that I'm cooking smells like sewage, or it smells like garbage," or, "I'm wandering through the grocery store and I come across the scent of the vegetables and fruit in the fresh food area, and I'm just getting a really foul odor that is obviously not linked with what my memory of that thing should smell like."

Interviewer: Other things I've heard it described is a chemical smell or taste, like ammonia, a bitter taste, burnt taste. Maybe even just people perceive it as bad breath.

Dr. Smith: Yeah, absolutely. The other common one, in addition to what you're describing, is actually a change in people's perception of their body odor, where it also smells more chemically, more foul. And people will also sometimes describe even a metallic smell or taste.

Interviewer: So describe to me how patients experience parosmia. So the way I understand kind of how it all begins is somebody gets COVID-19, they lose their sense of smell or taste. Are those the same things, by the way?

Dr. Smith: That's a great question. They are not the same. So your sense of taste is unique from your sense of smell. Taste is really comprised of kind of five to six main senses from your tongue. And those are things like sweet, salty, bitter, umami, versus your sense of smell is actually responsible for more of what people perceive as flavor. So the complexity of food, the flavor profile of food actually comes from your sense of smell, not from your sense of taste.

The story you're describing for how patients present with parosmia after COVID-19 is totally accurate. Usually what will happen is someone will come into my office, they'll tell me, "Sometime between three or four months ago, I got COVID-19. I was sick. My nose was stuffy and congested. My sense of smell was gone or decreased while I was sick." And associated with that, because your sense of smell is associated with your sense of taste, they'll tell me their sense of taste was disrupted.

And then afterwards, the rest of their COVID-19 symptoms got better in the majority of patients, but somewhere in that three- to four-month range, after that original illness, they tell me that they started to smell things wrong. And things that used to smell good don't smell good anymore. Food that used to taste good doesn't taste good anymore. It could be varied disruptive and disturbing to patients when they start to experience this.

Interviewer: Are there any factors that make somebody more likely to get parosmia more than somebody else?

Dr. Smith: There are a couple that we've identified. The first and most important is that if you lose your sense of smell or you have a reduction in your sense of smell while you have COVID-19, you do seem to be more likely to develop a disturbance in your sense of smell later, but you can still get it even if you didn't originally have smell loss.

And then the other things that we're seeing are that patients who are younger seem to be having a higher incidence of experiencing post-COVID smell disruption, and patients who are female also seem to have a higher incidence of post-COVID smell disruption.

Now, we don't really know why that is, but we are noticing it's higher in those groups. And unfortunately, that's not something that you can modify or change in your risk of developing this long term.

Interviewer: Parosmia can be caused by other things than COVID-19. So what is the diagnosis to ensure that that's what somebody has as a result of COVID?

Dr. Smith: So for us, the most important thing that we look at is the story that patients tell us. So when they come in and they tell us that they had a diagnosed episode of COVID-19 and that their change in sense of smell is temporally related to that infection, meaning that they occur in a similar time frame, that tells a pretty convincing story that their smell dysfunction is being caused by their COVID-19 infection.

There are other things that can cause changes in sense of smell and parosmia, including things like head trauma, medications, neurologic diseases, like seizures, Parkinson's, and other neurodegenerative diseases. And so usually your physician is going to ask you a whole bunch of questions to help rule out those other things even if you have a really convincing story of a COVID-19-related onset.

There are some things that we can do when it's not clear if someone actually has smell disruption, or if it's persisting. One of those things is called the UPSIT Test, which is an acronym describing a sense of smell test.

And here, you're given a booklet with a bunch of scratch and sniffs for testing your sense of smell. You'll go through all 40 of these smells and then you kind of pick from multiple-choice what you think the smell is. We can actually quantify and objectively tell you how disrupted your sense of smell is from that test based on your age and gender.

Interviewer: And then if somebody gets parosmia, how long does that generally last before a person starts smelling right again?

Dr. Smith: So most patients will continue to slowly improve with time, which is great news given how common that this is. And what we're seeing is that about 65% of patients will report a resolution in their abnormal or altered sense of smell by about 18 months. And by the time we get to two years, about 80% to 90% of patients will report that their disruption in sense of smell has resolved.

Interviewer: What are the treatments or therapies that are currently being used for treating parosmia? I understand there are not a lot of great evidence-based treatments out there right now, but can you talk about what we do know?

Dr. Smith: So you're right. There are not a lot of great evidence-based therapies to treat parosmia or olfactory dysfunction. One of the ones that we do have that actually has the most amount of evidence is something called olfactory retraining. And I explain this to my patients as kind of being like physiotherapy for your nose. What this entails is taking usually four common strong scents, and then practicing smelling them while you think about what that smell should smell like to try to help reform some of those normal responses of your nose and your brain to that smell stimulus.

And this has been shown to improve parosmia and hyposmia in patients with COVID-19. It can take about six to 12 weeks for patients to notice an impact, and up to 24 for them to kind of reach the maximal impact of doing that smell retraining.

It's described really well for people who are interested on a website called AbScent. That is also a good resource for patients experiencing these difficulties. So that's the one that we usually recommend patients try. It's very safe, very low risk. It does take some time to work, but it is supported by the evidence as potentially being useful.

Interviewer: Is that something that a patient can do on their own?

Dr. Smith: It absolutely is. And I would definitely recommend checking out that website if they're interested.

Interviewer: All right. And are there other potential treatments out there that have shown some promise?

Dr. Smith: So there are a whole bunch, and we're trying to figure out the best ones right now. The common ones that we're hearing about right now are things like Alpha-lipoic acid, which I know has been really popular on TikTok for a while. The thought process behind this being useful is that it is an antioxidant and it can potentially reduce inflammation, the same inflammation that we get from COVID-19 that could be causing damage to our sense of smell.

There is an older study from early on in the 2000s that showed some potential improvement in sense of smell on patients who were taking Alpha-lipoic acid. And there are physicians and scientists investigating this right now to see if it is able to be proven to be a beneficial therapy.

Now, the challenge with Alpha-lipoic acid is that taking it can actually cause some pretty significant side effects, including that it can lower your blood sugar. It's one of the medications that's sometimes used to treat diabetes. So if you already have low blood sugar or if you're taking diabetic medication, that can potentially conflict with your treatment or put you at risk for having a dangerously low blood sugar.

And similarly, like a lot of supplements out there, when you take them in higher doses, this can be associated with complications like insomnia, diarrhea, rashes, and fatigue. And so it's worth thinking about if you're potentially thinking about that therapy.

In addition to this, there are two other novel therapies that are being investigated in clinical trials. One is called a stellate ganglion block, and this is where usually a trained anesthesiologist or pain doctor would inject a medication into a little bundle of nerves in your neck, just behind your carotid artery. And this helps to block the nerve pathways that kind of are associated with this whole neurological pathway.

The stellate ganglion block itself is not a novel therapy. It's something that's been used for many years for chronic pain and for PTSD, but in the treatment of COVID-19-related parosmia, it is quite new.

There was a little case series, meaning that there was a study of just a small number of patients, that showed potential improvement. And based on this, we . . . not me personally, but within our community in rhinology, there is a clinical trial being started to see if stellate ganglion blocks do affect parosmia long term.

The last kind of clinical trial that I'll mention is a clinical trial looking at whether or not platelet-rich plasma injected into the mucosa or the area where the olfactory nerves live can improve your sense of smell after having COVID-19.

Platelet-rich plasma is kind of the leftovers of donated blood spun down into a really high concentrated, low volume mechanism. And platelet-rich plasma, or PRP, has been shown in some other areas of medicine, like veterinary medicine, to potentially have regenerative properties. And so there is a clinical trial ongoing about PRP and whether or not this can improve olfaction.

And for patients that are interested in these trials, there is a registry for clinical trials in North America. And this website is called clinicaltrials.gov. You can look to see if there's a provider in your area who's performing these types of studies if you're interested in that in the future.

Interviewer: What about salt water and nasal sprays? I've heard those as possible treatments. What are your thoughts on those?

Dr. Smith: I think that they're a great thing to try. So salt-water irrigations, and intranasal corticosteroids sprays, things like fluticasone or mometasone, are very safe therapies in the nose. And they've been shown in a variety of randomized control trials to be safe in treating a variety of conditions. So they're extremely low risk.

There is some evidence that using these therapies can potentially improve your sense of smell. The likelihood is low. So in the studies we're looking at, it's kind of been somewhere between 10% and 25% of patients that get an improvement while using them, but it's not zero. And the risk of using these medications is really low. So it is something I recommend in my practice to my patients.

Interviewer: Yeah, that risk versus benefit equation is really super important. Are there some things that people shouldn't do that you've been hearing people are trying because they actually could be very risky?

Dr. Smith: Yeah, that's a great question. And the short answer is yes. So the nasal mucosa, it's kind of unique in that it does a really good job of absorbing things that we put on top of it. And this means that if you're trialing home therapies or other natural remedies, a significant proportion of what you put in your nose can actually be absorbed into the bloodstream.

There are lots of different things being suggested or tried in the community as at-home remedies, and there's not a lot of great evidence for or against these. And some can potentially be dangerous to you. And so if you want to try something like that, I would really recommend you talk to your doctor about it first.

One of the anecdotal stories that we have is that earlier in this century, people thought that putting zinc nasal spray in the nose could potentially reduce the severity and duration of the common cold. And so this became a very popular treatment for a short period of time.

What we discovered was that these nasal sprays were actually causing direct toxicity to the olfactory pathway in the nose and causing a permanent and irreversible loss in sense of smell.

And so with that in mind, when we're going to try new things in the nose, we try to go about it as safely as possible. And if there are things you want to try, it is best to run it by your doctor first.

Interviewer: That's a good idea. Don't stick stuff up your nose that you don't necessarily know what it might do, even if it's natural. Natural doesn't necessarily mean safe.

Dr. Smith: Absolutely. Especially not in your nose.

Interviewer: Is there anything somebody can do beyond those treatments that might help them cope until they actually do recover?

Dr. Smith: Yes. So there are a few things that I recommend to my patients when we see these types of problems. The most effective thing that you can do right now, if you're struggling from parosmia, is actually lifestyle modifications. So as you start to identify what your triggers are, whether they be environmental, whether they be scents, whether they be food, trying to avoid those things that you don't have to experience that foul smell is really helpful.

And then similarly, when people are struggling with food, we have a couple recommendations to help improve your quality and quantity of eating. One of those things is to try to eat simpler or more bland meals. The more complex the aroma of a meal is, the more likely it seems to be to trigger that parosmia. And so the simpler you can make it for your brain as it's trying to interpret these smells, the better it seems to go.

And then along those lines, warm food has more of an aroma to it. You can kind of see that if you have this steaming plate of food coming out at you. That steam is what is carrying the sense of smell into our nose for us to receive it. Colder foods don't do that to the same extent. And so having your food at room temperature or even eating your food cold can help to improve your enjoyment of food if that's something that you're struggling with

Interviewer: Due to the lack of evidence-based treatments, is there a reason that a patient should go see a specialist for parosmia?

Dr. Smith: I mean, I'm biased because I'm a rhinologist. I'm a nose doctor. All I do and treat is the nose. And so I actually think it's an important part of my job to see patients who have parosmia after experiencing this alteration of their sense of smell so that we can, number one, take a good look in the nose, rule out those other things that we talked about earlier that could potentially be causing an alteration in the sense of smell for your good overall health.

And then number two, talk about the ways that you can manage this in the short term, and if there are any improving and changing therapies over time.

And last, but I think most importantly, I think it's really important to talk to patients and acknowledge how impactful this is and how bothersome it is for one of the things that you said earlier.

Often, people in their life who aren't experiencing this don't understand the severity of symptoms that come with parosmia. And so having a chance to talk about that, to validate what they're experiencing, to tell people, "Look, you're not crazy. This isn't in your head. This is a real thing," I actually think that's really important to do.

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Dr. Smith: When we're thinking about why viral illnesses can cause an alteration in your sense of smell, the analogy that I like to use is that your sense of smell is like a piano. It has a bunch of different receptors, a bunch of different keys, if you will. And the way we smell is by activating several of those receptors or keys, like playing a chord.

And what can happen after you've had COVID-19, a few things. One is that you can get actual damage to those keys or to the strings attached to them, the nerves that go up to your brain. And then that can lead to us, as we try to play that chord in the future, missing a few keys here and there. So rather than getting that nice chord, we have a discordant chord or something that doesn't sound or smell quite right, because the activation isn't consistent with what it was like before.

And so that's kind of the main reason that we think smell loss comes after having COVID-19, is because of that kind of local damage to the neuroepithelium, the skin inside of the nose where the nerves live, that alters the ability to activate all those receptors and the natural patterns that we need to link to our sense of smell.

And that's also why we think that olfactory training might be helpful, because it helps to rewire that new chord to what your brain remembers that smell should be, and helps us to kind of work back towards that more normal perception.