Chemical Senses

People often confuse smell loss with taste loss, so it is unclear how much gustatory function is reduced in patients self-reporting taste loss. Our pre-registered cross-sectional study design included an online survey in 12 languages with instructions for self-administering chemosensory tests with ten household items. Between June 2020 and March 2021, 10,953 individuals participated. Of these, 3,356 self-reported a positive and 602 a negative COVID-19 diagnosis (COVID+ and COVID-, respectively); 1,267 were awaiting test results (COVID?). The rest reported no respiratory illness and were grouped by symptoms: sudden smell/taste changes (STC, N=4,445), other symptoms excluding smell or taste loss (OthS, N=832), and no symptoms (NoS, N=416). Taste, smell, and oral irritation intensities and self-assessed abilities were rated on visual analog scales. Compared to the NoS group, COVID+ was associated with a 21% reduction in taste (95% Confidence Interval (CI): 15-28%), 47% in smell (95%-CI: 37-56%), and 17% in oral irritation (95%-CI: 10-25%) intensity. In all groups, perceived intensity of smell (r=0.84), taste (r=0.68), and oral irritation (r=0.37) was correlated. Our findings suggest most reports of taste dysfunction with COVID-19 were genuine and not due to misinterpreting smell loss as taste loss (i.e., a classical taste-flavor confusion). Assessing smell and taste intensity of household items is a promising, cost-effective screening tool that complements self-reports and helps to disentangle taste loss from smell loss. However, it does not replace standardized validated psychophysical tests.

The sense of taste is fundamental for survival as harmful substances can be discriminated and prevented from entering the body. Taste buds act as chemosensory sentinels and detect bitter, salty, sweet, sour, and umami substances and transmit signals to afferent nerve fibers. Whether a single gustatory nerve fiber selectively is responsive to a single taste modality (through taste receptor cell activation) is a point of contention in the field.. In the present study, we present a method for single cell RNA sequencing of gustatory geniculate ganglion neurons and compare the results obtained to two prior published works. Additionally, independent reanalysis of the raw data from these previous studies confirms molecular heterogeneity of ganglion neurons. Multiple gustatory clusters are found, and we compare cluster markers identified by the original works and those identified in the present study. Across all datasets and analyses, specific clusters show a high degree of correlation including a somatosensory cluster (Phox2b-, Piezo2+, Fxyd2+), a potential sweet-best cluster (Phox2b+, Spon1+, Olfm3+), and a potential sour-best cluster (Phox2b+, Penk+, Htr3a+). Additionally, a putative mechanosensitive gustatory cluster with an unknown functional role is identified (Phox2b+, Piezo2+, Calb1+). Other gustatory clusters (Phox2b+) are more varied across analyses, but are marked by Olfm3. Which, if any, clusters comprise umami-best, bitter-best, or salty-best fibers will require further study.

We recently discovered that the cystic fibrosis transmembrane conductance regulator protein (CFTR), which functions as a channel that transports chloride and bicarbonate across epithelial surfaces, is expressed in both human and murine TBCs, but how it functions in these cells remains unknown. We postulated that CFTR may impact peripheral taste signaling at the level of taste receptor-expressing cells of the taste bud. To begin to test this hypothesis, we assessed how pharmacological manipulation of CFTR could affect the functional responses of human fungiform taste bud cells to prototypical taste stimuli (e.g., bitter, sweet, fat) using single cell calcium imaging and neurotransmitter (ATP) release measurements. We first established the presence of CFTR in these cells using immunocytochemistry and RT-PCR. We next found that CFTR inhibition generally increased stimulus-evoked calcium responses but that the specific response parameters impacted varied across different stimuli, likely due to differences in signal transduction mechanisms and the involvement of store-operated calcium channels. For example, response amplitudes to bitter and sweet stimuli were significantly enhanced with no changes in the proportion of cells responding to these stimuli whereas the opposite trends were observed with a fatty acid stimulus. Additionally, bitter-evoked neurotransmitter release was significantly enhanced by CFTR inhibition, suggesting that this effect is reflected throughout the signal transduction cascade. Ongoing and future experiments are utilizing shRNA knockdown as well as intracellular and extracellular electrophysiology to further interrogate the impacts of CFTR. In addition to human TBCs, we have detected CFTR in mouse taste tissues. Moreover, we have mined mouse TBC RNA sequencing datasets to determine CFTR co-expression patterns to inform future cellular and behavioral experiments in mice. Taken together, these data suggest that CFTR can modulate the signaling output of the taste bud.

Olfactory and taste dysfunction are common symptoms of COVID-19 and post-acute COVID-19 syndrome, yet the effects of COVID-19 vaccines on chemosensory perception remain incompletely understood. This global, multilingual, online survey assessed post-vaccination changes in chemosensory function among individuals with and without COVID-19-related chemosensory impairment. Between May 2022 and August 2023, 2,955 responses were collected via convenience sampling, of which 1,352 were included in the analyses. Participants reported vaccination status, side effects, and chemosensory function before and after each vaccine dose. Pfizer-BioNTech accounted for 46.2% of doses, followed by Sputnik V (16.3%), Moderna (15.4%), AstraZeneca (8.9%), and Sinopharm (7.4%). More than 90% of participants reported no change in their general sense of smell or taste following vaccination, regardless of pre-existing chemosensory impairment. Among participants with qualitative chemosensory distortions (one-third of the sample), improvement was reported by 11-18% for parosmia, 20-29% for phantosmia, and 12-21% for taste distortion, depending on the vaccine dose, while worsening was reported by 3% or fewer. Side effects varied by vaccine type and were more frequent among individuals with worsened chemosensory symptoms. These findings suggest that COVID-19 vaccination is unlikely to adversely affect chemosensory function for most individuals. Given the observational design and reliance on self-reported data, the results should be interpreted cautiously. Future longitudinal studies using objective measures are needed to clarify these associations.

One of the entry routes of SARS-CoV-2 is the nasal epithelium. Although mounting evidence suggests the presence of olfactory dysfunction, and even anosmia, in patients with COVID-19, it is not clear whether these patients also suffer from other "nasal" symptoms that may influence their olfaction. A group of 35 patients with COVID-19 (and a control group matched in gender and age) were surveyed about the presence of a variety of nasal symptoms that may be associated to drastic perturbations experienced in the nasal cavity (e.g., "excessive dryness" and/or a continual sensation of having had a "nasal douche"). We used a cross-sectional, retrospective survey, targeted at the general population by means of non-quoted, non-random, snowball sampling. Symptoms were assessed with absence/presence responses. The possible association between two continuously distributed latent variables from categorical variables was estimated by means of polychoric correlations. More than 68% of the patients reported at least one "nasal" symptom. The clinical group also experienced "a strange sensation in the nose" and having excessive nasal dryness significantly more often than the control group. Fifty-two percent of the patients (but only 3% of the control group) reported a constant sensation of having had a strong nasal douche. Nasal symptoms predominantly co-occurred with anosmia/hyposmia, and ageusia/hypogeusia, appeared principally before or during the other symptoms of COVID-19, and lasted for twelve days, in average. The presence of these nasal symptoms, and their early occurrence, could potentially facilitate early diagnosis of COVID-19 and initial social distancing efforts.

Numerous flavor compounds are known to evoke sweet taste sensations, yet their direct interaction with the sweet taste receptor remains poorly understood. Traditionally, flavor-induced sweetness was attributed to aromatic properties rather than the taste qualities of these compounds. This study aims to elucidate whether the sweet taste receptor mediates flavor-induced sweet sensations by investigating the agonistic activities of 94 flavor compounds on cultured cells expressing the sweet taste receptor (T1R2/T1R3). The results demonstrated that cinnamaldehyde (CA) and p-methoxycinnamaldehyde (PMCA) activate the sweet taste receptor. These compounds not only induce the receptor response but also enhance receptor activity when combined with various sweeteners or sweet proteins. Due to PMCAs structural similarity to lactisole, a well-known negative allosteric modulator (NAM) of the sweet taste receptor interacting with the transmembrane domain (TMD) of T1R3, CA and PMCA are hypothesized to interact with the T1R3 TMD as ago-PAMs (agonists and positive allosteric modulators). Mutational analyses confirmed that CA and PMCA interact with the T1R3 TMD, with distinct binding sites compared to lactisole. Additionally, because of structural parallels between PMCA and lactisole, we investigated the structure-activity relationships among 79 compounds to determine whether they function as ago-PAMs or NAMs. Most compounds acted as inhibitors, while those with specific planar structures acted as ago-PAMs. In conclusion, this study identified CA and PMCA as novel ago-PAMs that interact with the T1R3 TMD of the sweet taste receptor. These findings significantly advance our understanding of how flavor compounds influence sweet taste perception at the molecular level. Significance StatementNumerous flavor compounds evoke sweet taste sensations, yet their interaction with the sweet taste receptor is not well understood. This study identifies cinnamaldehyde (CA) and p-methoxycinnamaldehyde (PMCA) as activators of the sweet taste receptor, interacting with the transmembrane domain (TMD) of T1R3. CA and PMCA also act as positive allosteric modulators of other sweeteners (ago-PAMs). We discovered two binding sites in the T1R3 TMD, with CA and PMCA binding to different sites than lactisole, a known negative allosteric modulator. These findings identify CA and PMCA as novel ago-PAMs and significantly advance our understanding of how flavor compounds influence sweet taste perception at the molecular level.

Background: Smell testing is increasingly recognized as essential in rhinology practice but remains underutilized because of time constraints and limited clinical resources. This study aimed to evaluate the performance (test-retest reliability, accuracy and test completion time) of a self-administered, digital version of SMELL-RS, a non-semantic test of olfactory resolution (SMELL-R) and sensitivity (SMELL-S). Methodology: We performed a test-retest reliability study in a tertiary care facility. We enrolled 100 subjects with and without smell dysfunction. The primary outcome measures were two replicates of olfactory test scores (SMELL-RS composite score, SMELL-R score, SMELL-S score). The secondary outcome measures were Sniffin Sticks score, test completion time, patient demographics, and other clinical characteristics (clinical symptoms, etiologies). Results: The SMELL-RS composite score was reliable (ICC=0.71; p<0.0001) and correlated with the Sniffin Sticks composite score (r=0.68; p<0.0001). Different etiologies have different magnitudes of smell loss as revealed by the SMELL-RS score. SMELL-S reduces misdiagnosis associated with Sniffin Sticks threshold tests. The average completion time of the olfactory resolution test (SMELL-R) was on average 5.9 minutes (SD=1.9), while the average completion time of the olfactory sensitivity test (SMELL-S) was 5.5 minutes (SD=2.7). This is two to three times faster than the corresponding Sniffin Sticks tests. Conclusions: SMELL-RS is a rapid, fully automated, reliable, and accurate olfactory test suitable for self-administration in a clinical setting.

BackgroundSigns of anosmia can help detect COVID-19 infection when testing for viral positivity is not available. Inexpensive mass-produced disposable olfactory sensitivity tests suitable for worldwide use might serve not only as a screening tool for potential infection but also to identify cases at elevated risk of severe disease as anosmic COVID-19 patients have a better prognosis. Methods and FindingsWe adopted paired crushable ampules with two concentrations of a standard test odorant (n-butanol) as standard of care in several clinics as community prevalence of COVID-19 infection waxed and waned. This was not a clinical trial; a chart review was undertaken to evaluate the operating characteristics and potential utility of the test device as RT-PCR testing became routine. The risk of anosmia was greater in COVID-19 patients. Olfactory sensitivity was concentration-dependent, decreased with aging, and was sex-dependent at the highest concentration. Hyposmia was detected across a wider age range than expected from the literature, and tests can be optimized to characterize different age groups. Conclusionsn-Butanol at 0.32 and 3.2% in crushable ampules can be used to characterize olfactory function quickly and inexpensively and thus has potential benefits in pandemic screening, epidemiology, and clinical decision-making.

SCENTinel - a rapid, inexpensive smell test that measures odor detection, intensity, identification, and pleasantness - was developed for population-wide screening of smell function. SCENTinel was previously found to screen for multiple types of smell disorders. However, the effect of genetic variability on SCENTinel test performance is unknown, which could affect the tests validity. This study assessed performance of SCENTinel in a large group of individuals with a normal sense of smell to determine the test-retest reliability and the heritability of SCENTinel test performance. One thousand participants (36 [IQR 26-52] years old, 72% female, 80% white) completed a SCENTinel test at the 2021 and 2022 Twins Days Festivals in Twinsburg, OH, and 118 of those completed a SCENTinel test on each of the festivals two days. Participants comprised 55% percent monozygotic twins, 13% dizygotic twins, 0.4% triplets, and 36% singletons. We found that 97% of participants passed the SCENTinel test. Test-retest reliability ranged from 0.57 to 0.71 for SCENTinel subtests. Broad-sense heritability, based on 246 monozygotic and 62 dizygotic twin dyads, was low for odor intensity (r=0.03) and moderate for odor pleasantness (r=0.4). Together, this study suggests that SCENTinel is a reliable smell test with only moderate heritability effects, which further supports its utility for population-wide screening for smell function.

Gustatory ability is an important marker of health status, including COVID-19 disease. We compare self-reporting with home and lab psychophysical "taste strips" tests in healthy subjects. The taste test consisted of paper strips impregnated with sweet, bitter, salty, or sour tastants, and with the trigeminal stimulus capsaicin, each in high and in low concentration. The test was carried out either in a controlled lab environment (74 participants, 47 women) with the strips being administered by the experimenter or self-administered by the participants at home (77 participants, 59 women). After self-reporting their subjective assessment of chemosensory ability, the participant identified the taste of each strip and rated intensity and pleasantness. Identification score, intensity, and pleasantness averaged over the 8 taste strips were similar between the lab and the home-administered tests. Self-rated taste ability did not correlate with any of these scores, but strongly correlated with self-rated smell ability in the lab group (r=0.73), and moderately correlated in the home group (r=0.51). Taste identification correlated with intensity ratings (r=0.63 lab, r=0.36 home) but not with the pleasantness ratings (r=-0.14 lab, r=0.1 home). The results of the taste strips test were similar in the lab and at home for healthy young participants and provide a baseline against which taste tests can be compared in future applications.

Inbred mouse strains differ in their postoral appetite stimulating response (appetition) to glucose and fructose. For example, C57BL/6J (B6) and FVB strains learn strong preferences for a flavor (CS+, e.g., cherry) paired with intragastric (IG) glucose infusions, but only FVB mice learned to prefer a CS+ paired with IG fructose infusions. Consistent with these findings, "tasteless" B6 knockout (KO) mice missing the taste signaling protein TRPM5 learn strong preferences for a CS+ added to glucose solution as well as for unflavored glucose but weak or no preferences for a fructose-paired CS+ or unflavored fructose. The present experiment reports that "tasteless" P2X2/P2X3 double-knockout (P2X2/3 DKO) mice, unlike TRPM5 KO mice, learned strong preferences for a CS+ mixed with fructose as well as for unflavored fructose. Whether differences in genetic backgrounds or other factors account for the fructose appetition displayed by P2X2/3 DKO mice but not TRPM5 KO mice remains to be determined.

Sensory systems translate physical stimuli from the environment--such as light, sound, or chemicals--into signals that the brain can interpret. Across these systems, the amplitude of a stimulus is represented by its perceived intensity. Although previous research has extensively studied how the brain represents physical stimuli, less is known about how it represents perceptual variables such as stimulus intensity. This is primarily due to the difficulty in measuring perceptual responses in animal models, where neural recordings are more accessible. In this study, we use mouse olfaction as a model system to develop a framework for measuring perceived odor intensity. We begin by employing a two-odor concentration classification task to demonstrate that both mice and humans assess stimulus amplitude using a common perceptual scale. We then show that this scale corresponds to intensity. Finally, we apply this method to determine isointense concentrations of different odorants in mice. Our approach offers a powerful tool for testing hypotheses about the neural mechanisms underlying perceived odor intensity, potentially enhancing our understanding of olfactory processing and its neural substrates.

Metabolic diseases such as diabetes and obesity are a growing healthcare concern, and their increasing rates are attributed to increased consumption of carbohydrate-rich diets and sugar-sweetened beverages. Fibroblast growth factor 21 (FGF21) is a complex metabolic regulator, and there is significant evidence that it may play a role in fructose metabolism, driving relative aversion to sweet taste. As such, we examined the relationship between FGF21 and the preferential intake of simple carbohydrates in mice, both as liquid solutions and as dietary additives. Genetic deletion of FGF21 or its obligate co-receptor {beta}-klotho (KLB) had no impact on preference for sugar sweetened solutions. FGF21 overexpression, however, substantially suppressed preference for fructose solutions, but had no effect on glucose or sucrose preference. Infusions of FGF21 also suppressed fructose preference specifically, an effect that was dependent on expression of KLB in the CNS. These results demonstrate that FGF21 creates sugar-specific taste aversion to fructose, which may be mediated by a KLB-dependent pathway in the brain. HighlightsO_LIFGF21 administration suppresses fructose preference in mice. C_LIO_LIPreference for glucose or sucrose is not affected by FGF21 administration. C_LIO_LIGenetic FGF21 deletion does not enhance fructose, glucose, or sucrose preference. C_LIO_LIFGF21 requires central {beta}-klotho expression to suppress fructose preference. C_LI

BackgroundDuring the COVID-19 pandemic, olfactory dysfunction (anosmia or hyposmia) has been reported by many patients and recognized as a prevalent and early symptom of infection. This finding has been associated with viral-induced olfactory neuron dysfunction rather than the nasal congestion typically found in cold- or flu-like states. In literature, the prevalence of anosmia varies from 15% to 85%, and the studies, in general, were based on the subjective evaluation of patients self-reports of loss of smell (yes or no question). In the present study, we quantitatively evaluated olfactory dysfunction and the prevalence of fever in symptomatic patients suspected of having COVID-19 using a scratch-and-sniff olfactory test and infrared temperature testing with RT-PCR as the gold-standard comparator method to diagnose COVID-19 infection. MethodsOutpatients had their forehead temperature checked with an infrared non-contact thermometer (temperature guns). After that, they received two olfactory smell identification test (SIT) cards (u-Smell-it; CT, USA) that each had 5 scent windows and were asked to scratch with a pencil and sniff each of the 10 small circles containing the microencapsulated fragrances and mark the best option on a response card. Nasopharyngeal swabs were then collected for Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) to determine if the patients were positive or negative for COVID-19 infection. We considered the number of hits (correct answers) [&le;] 5 as positive for loss of smell (LOS) in the olfactory test; [&ge;] 6 hits was considered negative for LOS (i.e. normal olfactory function). All data were analyzed using Excel and Matlab software. ResultsIn the present study, 165 patients were eligible for the olfactory test and nasopharyngeal swab collection RT-PCR. Five patients were excluded because of inconclusive PCR results (n=2) and missing data (n=3). A total of 160 patients completed all the protocols. The RT-PCR positivity rate for COVID-19 was 27.5% (n=44), and PCR+ patients scored significantly worse in the olfactory test (5.5{+/-}3.5) compared to RT-PCR-patients (8.2{+/-}1.8, p<0.001). 0/44 PCR+ patients presented with a fever ([&ge;]37.8{degrees}C). In contrast an olfactory SIT had a specificity of 94.8% (95% CI, 89.1 - 98.1), sensitivity of 47.7% (95% CI, 32.7 - 63.3), accuracy of 0.82 (95% CI, 0.75 - 0.87), positive predictive value of 77.8% (95% CI, 59.6 - 88.8), negative predictive value of 82.7% (85% CI, 78.7 - 86.7), and odds ratio of 16.7. ConclusionOur results suggest that temperature checking failed to detect COVID-19 infection, while an olfactory test may be useful to help identify COVID-19 infection in symptomatic patients.

BackgroundRecent surge of olfactory dysfunction in patients who were referred to ENT clinics and concurrent COVID-19epidemic in Iran motivated us to evaluate anosmic/hyposmic patients to find any relation between these two events. MethodsThis is a cross-sectional study with an online checklist on voluntary cases in all provinces of Iran between the 12th and 17th March, 2020. Cases was defined as self-reported anosmia/hyposmia in responders fewer than 4 weeks later (from start the of COVID-19 epidemic in Iran). Variables consist of clinical presentations, related past medical history, family history of recent respiratory tract infection and hospitalization. ResultsIn this study 10069 participants aged 32.5{+/-}8.6 (7-78) years, 71.13% female and 81.68% non-smoker completed online checklist. They reported 10.55% a history of a trip out of home town and 1.1% hospitalization due to respiratory problems recently. From family members 12.17% had a history of severe respiratory disease in recent days and 48.23% had anosmia/hyposmia. Correlation between the number of olfactory disorder and reported COVID-19 patients in all 31 provinces till 16th March 2020 was highly significant (Spearman correlation coefficient=0.87, p-Value<0.001). The onset of anosmia was sudden in 76.24% and till the time of filling the questionnaire in 60.90% of patients decreased sense of smell was constant. Also 83.38 of this patients had decreased taste sensation in association with anosmia. ConclusionsIt seems that we have a surge in outbreak of olfactory dysfunction happened in Iran during the COVID-19 epidemic. The exact mechanism of anosmia/hyposmia in COVID-19 patients needs further investigations.

Olfactory dysfunction following viral infection is a debilitating condition. Currently, the recommended treatment for olfactory dysfunction is olfactory training, a systematic and repeated exposure to odors over a prolonged period. A new tool has been proposed for olfactory training that present odors using nasal inserts rather than hand-held devices, to increase ease of training and thereby improving compliance and adherence to the training regimen. Here, we aimed to determine how olfactory training affects subjective experience of quality of life and olfactory function and potential differences training using regular versus the nasal insert setup. Using a randomized controlled design (N = 111), we investigated the effects of an 8-week olfactory training regimen using nasal inserts compared to standard care olfactory training in individuals with post-viral functional hyposmia. Subjective measures of quality of life as well as qualitative and quantitative olfactory function were assessed before and after the training regimen, and during a 1-year follow-up. Overall, participants showed significant and sustained improvements in both subjective olfactory function and quality of life following training. Critically, the nasal insert group demonstrated greater gains in social functioning and quantitative olfactory scores shortly after training, with enhanced olfactory benefits persisting at the 1-year follow-up. The magnitude of changes in quality of life was correlated with subjective olfactory improvement overall, with a stronger association for the nasal insert group. Thus, nasal insert training appears to enhance perceived olfactory function, which coincides with improved quality of life. Findings from this trial provide insight into the benefits of olfactory training on subjective functioning and quality of life, as well as the efficacy of nasal insert training in post-viral hyposmia.

The objective of this study was to design a short smell test adapted to the Venezuelan population using the UPSIT test as a reference.Methodology: Preliminary surveys were carried out in 2 groups of patients (1010 patients for each group) until obtaining the most frequently recognized odors and preferred values of that population. Normosmia, hyposmia and anosmia were normalized. The results of the new Venezuelan test were compared with the UPSIT test in 169 patients. Results: Sensitivity 73%, Specificity 100% and Positive predictive value of 100 with a diagnostic accuracy of 85,21%. Conclusions: short venezuelan smell test is safe and with reliable results in the diagnosis of olfactory alterations.

Since the onset of the COVID-19 infection, many patients reported sudden loss of smell (SLS). However, due to the lack of psychophysical testings, it remains difficult to know if these patients really have hyposmia or anosmia. Our group investigated the prevalence of anosmia and hyposmia in 28 COVID-19 patients and the potential association with nasal complaints.

The recovery period from post-COVID-19 smell and taste dysfunctions varies substantially, lasting from a few days to over a year. We aimed to assess the impact of COVID-19 on post-COVID-19 chemosensory sensitivity in a group of young convalescents of eastern/central European ancestry. We measured subjects smell and taste capabilities with a standard testing kit, Monell Flavor Quiz (MFQ), and collected surveys on COVID-19 history. During testing, subjects rated liking and intensity of six odor samples (galaxolide, guaiacol, beta-ionone, trimethylamine, phenylethyl alcohol, 2-ethyl fenchol) and six taste samples (sucralose, sodium chloride, citric acid, phenylthiocarbamide, menthol, capsaicin) on a scale from 1 (dislike extremely, or no intensity) to 9 (like extremely, or extremely intense). There was no statistical difference in intensity ratings or liking of any sample between subjects who reported a history of COVID-19 (n = 34) and those reporting no history (n = 40), independent of presence/absence or severity of smell/taste impairments (P > 0.05). Additionally, neither vaccination status (full vaccination or no vaccination) nor time from the COVID-19 onset (2-27 months) correlated with liking or intensity. These results suggest that most young adults who had COVID-19 recovered their sense of smell and taste.

BackgroundPost-COVID-19 olfactory dysfunction (PCOD) is a common sequela of SARS-CoV-2 infection, with some cases persisting beyond the acute phase. While prolonged PCOD has been considered primarily sensorineural, recent studies suggest that olfactory cleft (OC) obstruction may contribute to olfactory dysfunction (OD). This study aimed to investigate OC obstruction in prolonged PCOD compared to post-infectious olfactory dysfunction (PIOD) and assess its impact on olfactory function. Methodology/PrincipalWe retrospectively analysed sinus computed tomography scans of patients with prolonged PCOD and PIOD. OC obstruction was classified into absent (0%), mild (1-90%), and severe (>90%) types. The severity of OC obstruction was compared between PCOD and PIOD cases, and olfactory test results were analysed according to OC obstruction severity. ResultsA total of 87 PCOD patients and 67 PIOD patients were included. Mild and severe OC obstruction was more prevalent and severe in prolonged PCOD (mild: 35.6%, severe: 18.4%) than PIOD (mild: 13.4%, severe: 3%). Moreover, worsened olfactory function was found in PCOD patients with severe OC obstruction. In contrast, OC obstruction showed little association with olfactory function in PIOD patients. ConclusionsMild and Severe OC obstruction appear to be more common in prolonged PCOD. Moreover, severe OC obstruction may further impair olfactory function in PCOD patients. Conversely, severe OD in PIOD patients occurred independently of OC obstruction.