The year 2020 will go down in infamy due to the COVID-19 pandemic. The world experienced changes that were unimaginable and tragic. We’ve all learned (or increased our use of) words such as “social distancing,” “pandemic,” “quarantine,” “lockdown,” and “key workers,” to name a few. If you Google “COVID-19,” there are 6.5 trillion results. This respiratory virus, originating in China, had the power to shut down the world economy and force change to many aspects of our daily lives.
Fast-forward two years, and it seems as if we’re finally starting to see the light at the end of a very long tunnel. Unfortunately, there are still many COVID “long-haulers” suffering from lasting symptoms such as fatigue, shortness of breath, cough, joint and chest pain, and lost or distorted senses of smell and taste. Exactly how long these symptoms will last is still a mystery.
A mysterious condition: parosmia
A dear friend of mine tested positive for COVID-19 in December 2021. She had all the classic symptoms: cough, fever, difficulty breathing, and loss of taste and smell. Kristi is a registered nurse who spent several nights sitting in a chair watching her O2 stats, concerned that she would have to go to the hospital during the pandemic because she couldn’t breathe. Over time she got better, but now, over a year later, she is plagued with a mysterious condition called parosmia.
Olfactory training and COVID-19-related loss of smell
Loss of taste and smell: Distinguishing between COVID-19 and the common cold or flu
What exactly is parosmia? It’s “a change in the normal perceptions of odors, such as when the smell of something familiar is distorted, or something that normally smells pleasant now smells foul,” according to the National Institutes of Health (NIH).1 For a person with parosmia, many things that used to taste and smell pleasing are now the opposite—extremely unpleasant. Normally, taking a shower would be a refreshing experience, but now Kristi’s shower soap, which used to smell fresh and clean to her, smells like a wet, dirty dog. She can barely stomach the taste of foods that she loved in the past because they have a rotten, putrid smell. She says that some of the worst smells are dairy, flowers, any kind of meat, onions, garlic, fruit, and yogurt. Anything extremely sweet smells and tastes the most “normal.”
In most severe cases, parosmia can cause you to feel physically ill when your brain detects strong, unpleasant odors. Due to her altered sense of smell, Kristi is having difficulty eating a healthy diet, has experienced weight loss, and finds cooking dinner for her family stressful. All of this has taken a toll on her emotional well-being. COVID-19-related sensory upheaval has serious implications for food, eating, health, work, and well-being and for some is a profound existential assault disturbing their relationship to self, others, and the world.2
And parosmia isn’t triggered just by COVID-19—it’s an olfactory dysfunction characterized by a misperception of existing odors, and is more frequently detected in patients with postinfectious olfactory dysfunction.3 This may be seen secondary to head trauma, sinonasal abnormalities, neurological diseases, and idiopathic causes. Viruses can lead to olfactory dysfunction by causing damage to the upper respiratory tract and olfactory neurons.4 The literature states that parosmia that appears after COVID-19 is due to persistent degeneration of olfactory receptors.5
Some success with smell training
Current treatment methods for parosmia are vague, but there seems to be some success with “smell training.” According to a recent study published by the Laryngoscope, smell training did produce statistically significant improvement in COVID-19-induced parosmia over time. Smell training consists of sniffing at least four different odors every day for several months. Some common odors utilized in smell training include eucalyptus, lemon, rose, cinnamon, chocolate, coffee, lavender, honey, strawberry, and thyme. The subjects were tested on how well they could smell a variety of odors by sniffing different odors for 30 seconds twice a day. After following this routine for six months, it seemed that smell training can help the olfactory pathways start to regenerate and recover.4
Oral health implications
Dental professionals need to know that parosmia can potentially influence oral health. In searching through the literature, it’s still too early to tell what long-term effects parosmia might have on the dentition because enough time hasn’t passed for documented scientific evidence. Many people suffering from parosmia, including my friend Kristi, state that “extremely sweet is good.” Over time, this could be detrimental to oral health. It’s well-known that dental caries is a multifactorial disease that results from the interaction between a host (tooth surface), a substrate (food), the presence of bacterial biofilm (i.e., dental plaque), and time.6
If a patient is eating a diet high in extremely sweet foods, then the caries risk will also increase. For dental patients who express symptoms of parosmia, it’s very important to encourage daily plaque removal, swishing with water after eating, and fluoride application. If a patient is having difficulty with the taste of mint toothpaste, they may benefit from bubble-gum-flavored or a nonflavored fluoride toothpaste. Mouthwash is troublesome for my friend; she says it “tastes extremely bitter.” Recommending a fluoridated rinse such as Act for Kids may help introduce fluoride to the oral cavity. Some other dental products that may be beneficial during an unpleasant time may be:
Revitin toothpaste: Revitin is a prebiotic toothpaste that supports a healthy oral microbiome.
MI Paste/MI Paste Plus: MI Paste is a topical product that contains Recaldent (calcium, phosphate, and a milk-derived protein) and is applied after brushing and flossing.
BasicBites: These are caramel- or chocolate-flavored soft chews that contain arginine bicarbonate and xylitol, which will raise the oral pH and are cariostatic.
The worst-case scenario if a patient can’t tolerate any toothpaste or mouthwash containing fluoride would be to have them remove plaque mechanically with a wet brush and floss after eating. Depending on the severity of the parosmia, a referral to an ENT might be recommended to determine if there is an underlying cause, and possibly to start scent training. Ultimately, as oral health-care professionals, we should instill in our patients a way to reduce bacterial levels, promote a neutral oral pH, and promote mineral exchange between saliva and teeth using fluoride, calcium, and phosphate.
Complications of COVID-19 continue to be identified. Current research doesn’t accurately address the seriousness of parosmia and other long-term side effects of COVID-19 because enough time hasn’t passed. The impact of smell and taste alteration is concerning for those experiencing this because eating is normally a pleasurable experience, and many social events center around the dinner table or a restaurant. I can’t imagine not being able to eat some of the comfort foods that I’ve grown to love over the years. Kristi has expressed that she is “grieving” the loss of being able to gain pleasure from food, and I am hopeful that with scent training, she’ll regain her normal sense of smell.
Editor's note: This article appeared in the June 2022 print edition of RDH magazine. Dental hygienists in North America are eligible for a complimentary print subscription. Sign up here.
- Parosmia. National Institute on Deafness and Other Communication Disorders. National Institutes of Health (NIH). Accessed April 2, 2022. www.nidcd.nih.gov/glossary/parosmia
- Burges Watson DL, Campbell M, Hopkins C, Smith B, Kelly C, Deary V. Altered smell and taste: anosmia, parosmia and the impact of long Covid-19. PLoS ONE. 2021;16(9): e0256998. doi:10.1371/journal.pone.0256998
- Duyan M, Ozturan IU, Altas M. Delayed parosmia following SARS-CoV-2 infection: a rare late complication of COVID-19. SN Compr Clin Med.2021;3(5):1200-1202. doi:10.1007/s42399-021-00876-6
- Liu DT, Sabha M, Damm M, Philpott C, Oleszkiewicz A, Hähner A, Humme T. Parosmia is associated with relevant olfactory recovery after olfactory training. Laryngoscope. 2021;131(3):618-623. doi:10.1002/lary.29277
- Khalifah W, Damanhouri B, Abushal B, Marglani O, Alharbi B, et al. Persistent parosmia caused by COVID-19 infection: An emerging symptom. Cureus. 2021;13(11):e19921. doi:10.7759/cureus.19921
- Nelson T, Velan E. Evaluating caries risk. Dimens Dent Hyg. February 2014. Accessed April 2, 2022. dimensionsofdentalhygiene.com/article/evaluating-caries-risk/