Multiple Chemical Sensitivity: It's time to catch up to the science

Multiple chemical sensitivity (MCS) is a complex medical condition associated with low dose chemical exposures. MCS is characterized by diverse features and common comorbidities, including fibromyalgia, cough hypersensitivity, asthma, and migraine, and stress/anxiety, with which the syndrome shares numerous neurobiological processes and altered functioning within diverse brain regions. Predictive factors linked to MCS comprise genetic influences, gene-environment interactions, oxidative stress, systemic inflammation, cell dysfunction, and psychosocial influences. The development of MCS may be attributed to the sensitization of transient receptor potential (TRP) receptors, notably TRPV1 and TRPA1. Capsaicin inhalation challenge studies demonstrated that TRPV1 sensitization is manifested in MCS, and functional brain imaging studies revealed that TRPV1 and TRPA1 agonists promote brain-region specific neuronal variations. Unfortunately, MCS has often been inappropriately viewed as stemming exclusively from psychological disturbances, which has fostered patients being stigmatized and ostracized, and often being denied accommodation for their disability. Evidence-based education is essential to provide appropriate support and advocacy. Greater recognition of receptor-mediated biological mechanisms should be incorporated in laws, and regulation of environmental exposures.

An olfactory perceptual fingerprint in people with olfactory dysfunction due to COVID-19

The sense of smell is based on sensory detection of the molecule(s), which is then further perceptually interpreted. A possible measure of olfactory perception is an odor-independent olfactory perceptual fingerprint (OPF) defined by Snitz et al. We aimed to investigate whether OPF can distinguish patients with olfactory dysfunction (OD) due to coronavirus disease (COVID-19) from controls and which perceptual descriptors are important for that separation. Our study included 99 healthy controls and 41 patients. They rated 10 odors using 8 descriptors such as "pleasant," "intense," "familiar," "warm," "cold," "irritating," "edible," and "disgusting." An unsupervised machine learning method, hierarchical cluster analysis, showed that OPF can distinguish patients from controls with an accuracy of 83%, a sensitivity of 51%, and a specificity of 96%. Furthermore, a supervised machine learning method, random forest classifier, showed that OPF can distinguish patients and controls in the testing dataset with an accuracy of 86%, a sensitivity of 64%, and a specificity of 96%. Principal component analysis and random forest classifier showed that familiarity and intensity were the key qualities to explain the variance of the data. In conclusion, people with COVID-19-related OD have a fundamentally different olfactory perception.

Body odor disgust sensitivity (BODS) is related to extreme odor valence perception

Odors are important disease cues, and disgust sensitivity to body odors reflects individual differences in disease avoidance. The body odor disgust sensitivity (BODS) scale provides a rapid and valid assessment of individual differences. Nevertheless, little is known about how individual differences in BODS might correlate with overall odor perception or how it is related to other differences in emotional reactivity (e.g., affect intensity). We investigated how BODS relates to perceptual ratings of pleasant and unpleasant odors. We aggregated data from 4 experiments (total N = 190) that were conducted in our laboratory, and where valence and intensity ratings were collected. Unpleasant odors were body-like (e.g., sweat-like valeric acid), which may provide disease cues. The pleasant odors were, in contrast, often found in soap and cleaning products (e.g., lilac, lemon). Across experiments, we show that individuals with higher BODS levels perceived smells as more highly valenced overall: unpleasant smells were rated as more unpleasant, and pleasant smells were rated as more pleasant. These results suggest that body odor disgust sensitivity is associated with a broader pattern of affect intensity which causes stronger emotional responses to both negative and positive odors. In contrast, BODS levels were not associated with odor intensity perception. Furthermore, disgust sensitivity to odors coming from external sources (e.g., someone else's sweat) was the best predictor of odor valence ratings. The effects were modest in size. The results validate the BODS scale as it is explicitly associated with experimental ratings of odor valence.

Motor Cortex Response to Pleasant Odor Perception and Imagery: The Differential Role of Personality Dimensions and Imagery Ability

Background

Neuroimaging studies have shown a complex pattern of brain activation during perception of a pleasant odor and during its olfactory imagery. To date, little is known regarding changes in motor cortex excitability during these tasks. Bergamot essential oil (BEO) is extensively used in perfumes and cosmetics for its pleasantness. Therefore, to further our understanding of the human sense of smell, this study aimed to investigate the effect of perception and imagery of a pleasant odor (BEO) on motor cortex using Transcranial magnetic stimulation (TMS).

Materials and Methods

We examined the primary motor cortex (M1) excitability during perception of a pleasant odor (BEO) or perception of odorless saline (experiment 1). Furthermore, we tested the effect of olfactory imagery (OI) of BEO on corticospinal excitability (experiment 2). The increase in motor evoked potential (MEP) amplitude was correlated with personality dimensions scores, pleasantness, vividness, and general imagery ability.

Results

The results indicate that the corticospinal excitability changed after both perception and imagery of a pleasant odor (BEO). The correlation analysis shows an association with neuroticism personality trait (experiment 1) and with general olfactory imagery ability (experiment 2).

Conclusion

Both perception of a pleasant odor and its olfactory imagery modulate motor cortex excitability. The enhanced brain activation is affected by specific individual characteristics. Overall, our findings provide physiological evidence for a complex interaction between the olfactory and motor systems.

Olfactory Virtual Reality: A New Frontier in the Treatment and Prevention of Posttraumatic Stress Disorder

This perspective piece reviews the clinical condition of posttraumatic stress disorder (PTSD), which is currently increasing due to the COVID-19 pandemic, and recent research illustrating how olfaction is being incorporated into virtual reality (VR) platforms. I then discuss the latest work examining the potential of olfactory virtual reality (OVR) for the treatment of PTSD. From this foundation I suggest novel ways in which OVR may be implemented in PTSD therapy and harnessed for preventing the development of PTSD. Perceptual and chemical features of olfaction that should be considered in OVR applications are also discussed.

Chemical Intolerance Is Associated With Altered Response Bias, not Greater Sensory Sensitivity

Chemical intolerance is a surprisingly prevalent condition or affliction characterized by adverse reactions to low levels of chemical, often odorous stimulation. Sufferers often assume that their plight is due to an uncommon sensory acuteness, yet studies repeatedly fail to reveal altered detection thresholds. Here, we investigated whether self-reported chemical intolerance is associated with altered sensory sensitivity or response bias. The sensory acuity (sensitivity; A) and sensory decision rule (criterion; B) to n-butanol was assessed using the method of constant stimuli in 82 participants with different degrees of chemical intolerance (low to high). Higher self-reported chemical intolerance was associated with a lower criterion, but not with sensitivity.

Multisensory environmental sensitivity in patients with chronic tinnitus

OBJECTIVE

The study aimed at investigating the sensitivity to noise and chemosensory environmental stressors as well as the relation to perceived stress, depression and anxiety in subjects with chronic tinnitus as compared to subjects without tinnitus.

METHODS

We included 75 subjects with chronic tinnitus and 75 age and sex-matched subjects without tinnitus. Standardized questionnaires assessing the level of distress and impairment of quality of life caused by tinnitus, perceived level of stress, anxiety and depression, environmental noise and chemosensory sensitivity were used. A subgroup of 27 subjects with chronic tinnitus and 20 age-matched subjects without tinnitus underwent testing of olfactory function with the Sniffin' Sticks test and testing of intranasal trigeminal function using CO2 thresholds.

RESULTS

Our data confirmed the increased environmental noise sensitivity (NSS) in patients with tinnitus. Furthermore, we observed an increased environmental chemosensory sensitivity (CSS), but no difference in measured chemosensory function. Subjects with tinnitus showed also significant higher levels of perceived stress, anxiety and depression and those symptoms partially correlated to CSS and NSS. Predictors of both NSS and CSS results were the presence / absence of tinnitus and high anxiety levels while neither stress nor depression were found as predicting variables.

CONCLUSIONS

The results suggest that chronic tinnitus is related to a multisensory environmental hypersensitivity. Anxiety seems to be a predictor of this environmental vulnerability.

Olfactory-Related Quality of Life in Multiple Chemical Sensitivity: A Genetic-Acquired Factors Model

Genetic polymorphisms as well as environmental exposures to chemical compounds, iatrogenic, psychological, and physical trauma may play a pathophysiological role in multiple chemical sensitivity (MCS) olfactory complaints, given that xenobiotic metabolism is influenced by sequence variations in genes of metabolizing enzymes. Thus, the aim of the present study was to depict-by means of multiple regression analysis-how different genetic conditions, grouped according to their function as well as clinical background and environmental exposure may interfere with those olfactory complaints referred by MCS patients. Therefore, MCS patients after gene polymorphism sequencing, the olfactory-related quality of life score-calculated by means of the Questionnaire of Olfactory Disorder in forty-six MCS patients-have been found to significantly rely on the phase I and II enzymes score and exposure to previous compounds and surgical treatments. The present work-implementing for the first time a genetic-acquired factors model on a regression analysis-further reinforces those theories, positing MCS as a complex, multifactorial, disease in which the genetic risk related to phase I and II enzymes involved in xenobiotic detoxification, olfactory, and neurodegenerative diseases play a necessary, but probably not sufficient role, along the pathophysiological route of the disease.

Odor sensitivity impairment: a behavioral marker of psychological distress?

OBJECTIVE

Enhanced odor sensitivity, particularly toward threat-related cues, may be adaptive during periods of danger. Research also suggests that chronic psychological distress may lead to functional changes in the olfactory system that cause heightened sensitivity to odors. Yet, the association between self-reported odor sensitivity, objective odor detection, and affective psychopathology is currently unclear, and research suggests that persons with affective problems may only be sensitive to specific, threat-related odors.

METHODS

The current study compared adults with self-reported odor sensitivity that was described as functionally impairing (OSI; n = 32) to those who reported odor sensitivity that was non-impairing (OS; n = 17) on affective variables as well as quantitative odor detection.

RESULTS

Increased anxiety sensitivity, trait anxiety, depression, and life stress, even while controlling for comorbid anxiety and depressive disorders, was found for OSI compared to OS. While OSI, compared to OS, demonstrated only a trend increase in objective odor detection of a smoke-like, but not rose-like, odor, further analysis revealed that increased detection of that smoke-like odor was positively correlated with anxiety sensitivity.

CONCLUSION

These findings suggest that persons with various forms of psychological distress may find themselves significantly impaired by an intolerance of odors, but that self-reported odor sensitivity does not necessarily relate to enhanced odor detection ability. However, increased sensitivity to a smoke-like odor appears to be associated with sensitivity to aversive anxiogenic stimuli. Implications for the pathophysiology of fear- and anxiety-related disorders are discussed.

Exploring the science, safety, and benefits of air care products: perspectives from the inaugural air care summit

Seventy-one percent of US households purchase air care products. Air care products span a diverse range of forms, including scented aerosol sprays, pump sprays, diffusers, gels, candles, and plug-ins. These products are used to eliminate indoor malodors and to provide pleasant scent experiences. The use of air care products can lead to significant benefits as studies have shown that indoor malodor can cause adverse effects, negatively impacting quality of life, hygiene, and the monetary value of homes and cars, while disproportionately affecting lower income populations. Additionally, studies have also shown that scent can have positive benefits related to mood, stress reduction, and memory enhancement among others. Despite the positive benefits associated with air care products, negative consumer perceptions regarding the safety of air care products can be a barrier to their use. During the inaugural Air Care Summit, held on 18 May 2018 in the Washington, DC, metropolitan area, multidisciplinary experts including industry stakeholders, academics, and scientific and medical experts were invited to share and assess the existing data related to air care products, focusing on ingredient and product safety and the benefits of malodor removal and scent. At the Summit's completion, a panel of independent experts representing the fields of pulmonary medicine, medical and clinical toxicology, pediatric toxicology, basic science toxicology, occupational dermatology and experimental psychology convened to review the data presented, identify potential knowledge gaps, and suggest future research directions to further assess the safety and benefits of air care products.

Survey of the effect of odour impact on communities

In the context of environmental malodour, surveys are valuable as they allow for the relatively detailed analysis of multiple factors pertaining to odour perception and subsequent reaction. However, the causes for an individual to experience odour impact while a neighbour will not are still not understood. The goal of this current survey design was to consolidate varying research paths for surveys within the environmental odour research space. This survey investigated the area of effect for wastewater treatment plants by using stratified random sampling techniques that radiated from the industrial areas. Additionally, this survey provided a "non-alerted" response to environmental malodour that represents a step forward for ecological validity. We found a small number of items relating to odour annoyance and home ownership that can be used in order to predict odour impact for individual community members. However, we also did not find any relationship with odour impact and perceived control. This survey design and analysis reconciles the varied approaches towards community surveys administered in prior literature, as well as providing information to improve future community engagement policies.

Gender differences in influences of temperament on olfactory reactivity and awareness

Children's olfactory performance is associated with temperament but whether there is a link with olfactory reactivity and awareness is not known. In adults negative affectivity is linked to reactivity to environmental odours but it is not clear whether these associations extend to children. We aimed to investigate the effect of temperamental factors on olfactory reactivity and awareness. In so doing, we controlled for the effect of parenting styles on temperamental assessment and of verbal fluency on children's olfactory reactivity and awareness. We hypothesised that children with a high degree of negative affectivity would show greater olfactory reactivity and awareness. 129 children (62 boys, mean age 6.83 ± 0.40 years) were interviewed about their olfactory reactivity and awareness in everyday life using the established Children's Olfactory Behavior in Everyday Life questionnaire (COBEL). Parents assessed their child's temperament using the 94-item short form of the Children's Behavior Questionnaire. We found that the relationship between negative affectivity and total COBEL scores varied between the genders: there was a positive, medium to large effect in boys and a negative, small one in girls. Future studies could include behavioural observations of temperament and olfactory reactivity and awareness.

Self-Ratings of Olfactory Performance and Odor Annoyance Are Associated With the Affective Impact of Odor, but Not With Smell Test Results

Our aim was to explore factors potentially associated with subjective (self-rated) and objective (measured using the Sniffin' Sticks Extended test) olfactory performance in the general population without olfactory disorders. We studied associations between olfactory performance and how important odors were in determining liking for new places, things, and people (measured using the Affective Impact of Odor scale) and the average annoyance caused by odors in 117 adults (83 women, 34 men; age 18-69 years, mean age 32 years). In a subset of 44 participants, we also studied associations between olfactory performance and spice odor identification task scores (14 odors) and the number of herbs and spices consumed. Self-rated olfactory acuity and odor-related annoyance were associated with the Affective Impact of Odor scores, but neither correlated with the smell test results. Instead, the number of spices consumed correlated with spice odor identification score ( r = .50) and the identification (but not threshold nor discrimination) subscore of the Sniffin' Sticks test ( r = .49). Our results suggest that a tendency to perceive odors in affective terms may be associated with overestimation of olfactory abilities and that recurrent exposure to a large variety of spice odors may improve performance on odor identification.

Interindividual differences in chemosensory perception: Toward a better understanding of perceptual ratings during chemical exposures

Perceptions that arise from stimulation of olfactory and trigeminal receptors in the nasal cavity guide the evaluation of chemical environment in humans. Strong interindividual differences in these assessments may be attributed to nonsensory factors such as gender, anxiety, and chemical sensitivity. Knowledge regarding the influence of these factors originates mainly from basic odor research using short-term exposure scenarios. In situations with continuous chemical exposures-common in the working environment-their impact is less clear. To investigate their role during the exposure to workplace chemicals, 4-hour experimental exposure studies (total N = 105) using nine different airborne chemicals were summarized. In each study, subjects evaluated a single chemical in a controlled environment by rating five chemosensory perceptions, including odor intensity, disgust, annoyance, pungency, and burning, several times during occupational limit and low exposures. It was investigated whether the effects of trait-like modulators, such as anxiety and self-reported chemical sensitivity, depend on exposure-related factors and gender. Trait-like modulators markedly affected ratings by women, but not men. Highly anxious women reported more intense annoyance and disgust than less anxious women. Stronger self-reported chemical sensitivity was associated with increased ratings of pungency and burning in women exposed to occupational limit concentrations. This study demonstrates that a complex interplay of exposure-related factors, gender, and trait-like individual differences affects perceptual ratings during continuous chemical exposure. It seems necessary to incorporate the assessment of specific as well as general trait-like modulators into future experimental exposure studies.

Possible relation between olfaction and anxiety in healthy subjects

AIMS

While olfaction is a sense closely associated with the limbic system and emotions, the relation between emotional status and olfactory functioning has not been well documented. This study aimed to examine the possible effect of anxiety on olfaction in healthy subjects.

METHODS

We investigated the effect of state and trait anxiety on the detection and recognition thresholds for five different odors in 124 healthy subjects (62 men and 62 women, mean age = 27.2 years) using a T&T olfactometer.

RESULTS

While the influences of age, socioeconomic status, IQ, and smoking history on olfaction were not significant, women had a lower recognition threshold for the odor of sweet fruit and a higher detection threshold for that of rotten food as compared with men. Both state and trait anxiety ratings were significantly associated with reduced olfactory ability, especially for identification of rose odor.

CONCLUSIONS

These findings suggest that emotional status affects olfactory functioning in healthy subjects. Our findings may also partly explain the mild olfactory impairment reported in clinical conditions, such as anxiety disorders.

Noise and somatic symptoms: A role for personality traits?

OBJECTIVES

We investigated the role of a stress-sensitive personality on relations between noise, noise annoyance and somatic symptom reporting. First, we investigated the cross-sectional association of road traffic noise exposure and somatic symptoms, and its modification by hostility and vulnerability to stress. Second, we investigated the cross-sectional association of noise annoyance from eight sources (e.g. road traffic, aircraft, neighbours) and somatic symptoms, and it's confounding by hostility and vulnerability to stress.

METHODS

Data were obtained from LifeLines, a general population cohort from the Netherlands. Road traffic noise was estimated using the Common Noise Assessment Methods in Europe (CNOSSOS-EU) noise model. Noise annoyance, hostility, vulnerability to stress, and somatic symptoms were assessed with validated questionnaires.

RESULTS

Poisson regression models adjusted for demographic and socioeconomic variables indicated no association of noise exposure and somatic symptoms (incidence rate ratio (IRR) 1.001; 95% confidence interval (CI) 1.000-1.001; n=56,937). Interactions of noise exposure and hostility and vulnerability to stress were not statistically significant. Small positive associations were found for noise annoyance from each of the eight sources and somatic symptoms, when adjusted for demographic and socioeconomic variables (e.g. for road traffic noise annoyance IRR 1.014, 95% CI 1.011-1.018; n=6177). Additional adjustment for hostility and vulnerability to stress resulted in small decreases of the IRRs for noise annoyance from each of the eight sources, but the associations remained statistically significant.

CONCLUSIONS

Personality facets hostility and vulnerability to stress did not modify the relation between road traffic noise exposure and somatic symptom reporting, or confound relations between noise annoyance and symptoms.

Chemosensory perception, symptoms and autonomic responses during chemical exposure in multiple chemical sensitivity

PURPOSE

Multiple chemical sensitivity (MCS) is a prevalent medically unexplained symptom characterized by symptom reactions to everyday chemical exposure below hygienic thresholds. The aim of this study was to investigate the expressions of hyper-reactivity in MCS during whole-body exposure to low concentrations of the odorant n-butanol.

METHODS

We exposed 18 participants with MCS and 18 non-ill controls to a low concentration of the odorant n-butanol using an exposure chamber. The first 10 min constituted blank exposure, after which the n-butanol concentration increased and reached a plateau at 11.5 mg/m(3).

RESULTS

MCS participants, compared with controls, reported greater perceived odor intensities, more unpleasantness to the exposure and increasing symptoms over time. MCS participants also expressed higher pulse rate and lower pulse rate variability than controls did. No group differences were found for breathing rate or tonic electrodermal activity responses.

CONCLUSIONS

We conclude that MCS sufferers differ from healthy controls in terms of autonomic responses, symptoms and chemosensory perception during chemical exposure.

Cortical activity during olfactory stimulation in multiple chemical sensitivity: a (18)F-FDG PET/CT study

PURPOSE

To investigate the differences in brain glucose consumption during olfactory stimulation between subjects affected by multiple chemical sensitivity (MCS) and a group of healthy individuals.

METHODS

Two (18)F-FDG PET/CT scans were performed in 26 subjects (6 men and 20 women; mean age 46.7 ± 11 years) with a clinical diagnosis of MCS and in 11 healthy controls (6 women and 5 men; mean age 45.7 ± 11 years), the first scan after a neutral olfactory stimulation (NS) and the second after a pure olfactory stimulation (OS). Differences in (18)F-FDG uptake were analysed by statistical parametric mapping (SPM2).

RESULTS

In controls OS led to an increase in glucose consumption in BA 18 and 19 and a reduction in glucose metabolism in BA 10, 11, 32 and 47. In MCS subjects, OS led to an increase in glucose consumption in BA 20, 23, 18 and 37 and a reduction in glucose metabolism in BA 8, 9 and 10.

CONCLUSION

The results of our study suggest that cortical activity in subjects with MCS differs from that in healthy individuals during olfactory stimulation.

Research on odor interaction between aldehyde compounds via a partial differential equation (PDE) model

In order to explore the odor interaction of binary odor mixtures, a series of odor intensity evaluation tests were performed using both individual components and binary mixtures of aldehydes. Based on the linear relation between the logarithm of odor activity value and odor intensity of individual substances, the relationship between concentrations of individual constituents and their joint odor intensity was investigated by employing a partial differential equation (PDE) model. The obtained results showed that the binary odor interaction was mainly influenced by the mixing ratio of two constituents, but not the concentration level of an odor sample. Besides, an extended PDE model was also proposed on the basis of the above experiments. Through a series of odor intensity matching tests for several different binary odor mixtures, the extended PDE model was proved effective at odor intensity prediction. Furthermore, odorants of the same chemical group and similar odor type exhibited similar characteristics in the binary odor interaction. The overall results suggested that the PDE model is a more interpretable way of demonstrating the odor interactions of binary odor mixtures.

Brain responses to olfactory and trigeminal exposure in idiopathic environmental illness (IEI) attributed to smells -- an fMRI study

OBJECTIVE

Idiopathic environmental intolerance (IEI) to smells is a prevalent medically unexplained illness. Sufferers attribute severe symptoms to low doses of non-toxic chemicals. Despite the label, IEI is not characterized by acute chemical senses. Theoretical models suggest that sensitized responses in the limbic system of the brain constitute an important mechanism behind the symptoms. The aim was to investigate whether and how brain reactions to low-levels of olfactory and trigeminal stimuli differ in individuals with and without IEI.

METHODS

Brain responses to intranasally delivered isoamyl acetate and carbon dioxide were assessed in 25 women with IEI and 26 non-ill controls using functional magnetic resonance imaging.

RESULTS

The IEI group had higher blood-oxygenated-level-dependent (BOLD) signal than controls in the thalamus and a number of, mainly, parietal areas, and lower BOLD signal in the superior frontal gyrus. The IEI group did not rate the exposures as more intense than the control group did, and there were no BOLD signal differences between groups in the piriform cortex or olfactory regions of the orbitofrontal cortex.

CONCLUSIONS

The IEI reactions were not characterized by hyper-responsiveness in sensory areas. The results can be interpreted as a limbic hyperreactivity and speculatively as an inability to inhibit salient external stimuli.

Multiple chemical sensitivity worsens quality of life and cognitive and sensorial features of sense of smell

Multiple chemical sensitivity (MCS) is characterized by a loss of tolerance to a variety of environmental chemicals. Multiple chemical sensitivity is frequently triggered by exposure to chemical agents, especially insecticides. The aim of the study was to measure the sense of smell and quality of life in patients with MCS compared to the control group. We studied the sense of smell, both sensitive and sensorial characteristics, in female patients with MCS (n = 58, mean 50.5 ± 8.5 years) and healthy female volunteers without rhinosinusal pathologies (n = 60, mean age 46 ± 10.2 years). Olfactometry (Barcelona Smell Test 24/BAST-24), sinonasal symptoms (visual analogue scale/VAS 0-100 mm), and quality of life (Quick Environmental Exposure and Sensitivity Inventory/QEESI) were assessed. Multiple chemical sensitivity patients showed a significant impairment in smell identification (19 ± 12 %; p > 0.05) and forced choice (62 ± 18 %; p > 0.05), but not in smell detection (96 ± 4 %) compared to the control group. Multiple chemical sensitivity patients reported more odours as being intense and irritating and less fresh and pleasant when compared with the control group. Patients scored a high level (40-100) on QEESI questionnaire (symptom severity, chemical intolerances, other intolerances, life impact). In MCS patients, total symptom intensity (VAS/0-700 mm) score was 202 ± 135, while disease severity score was 80 ± 23. The most frequent symptoms were itching and posterior rhinorrhea. Multiple chemical sensitivity patients have an impairment in smell cognitive abilities (odour identification and forced choice, but not for detection) with increased smell hypersensitivity and poor quality of life.

Intranasal Administration of Hyaluronan as a Further Resource in Olfactory Performance in Multiple Chemical Sensitivity Syndrome

Multiple chemical sensitivity (MCS) is a relatively common clinical diagnosis in western populations and its symptoms (i.e. dysosmia) are mainly triggered by chemical compounds, such as common odorants. The aim of this study was to test the effect of intranasal administration of hyaluronic acid (HA) on odour threshold and related quality of life in MCS syndrome. Two randomized groups of MCS patients received 30 days' administration of either a nasal spray (Ialumar®) containing HA [HA group (HAG); n=29] or only physiological solution [PS group (PG); n=30]. Both groups were investigated using the “Sniffin' Sticks” test (SST) battery, Questionnaire of Olfactory Disorder (QOD) and Zung Anxiety Scale (SAS) before randomization and after treatment. Paired t-test analysis found a statistically significant reduction in odour threshold (OT) and an improvement in QOD and SAS between pre- and post-treatment results only in the HAG. Furthermore, positive correlations were found between the OT reduction, SAS and QOD improvement. Thus, intranasal administration of HA could be suggested as a further well-tolerated resource in alleviating MCS olfactory discomfort.

Increased odor detection speed in highly anxious healthy adults

Anxiety can either impair or enhance performance depending on the context. Increased sensitivity to threat seems to be an important feature of sensory processing in anxiety since anxious individuals tend to be more attentive to threatening visual stimuli. Evidence of anxiety effects in olfaction is rare; though alterations of olfactory performance in psychiatric patients and some effects of trait and state anxiety on olfactory performance have been reported. Our main objective was thus to investigate whether olfactory processing speed varies as a function of trait anxiety levels. We additionally investigated a possible preferential bias for unpleasant odors in highly anxious participants. Thirty-eight healthy adults participated in a simple odor detection task, where response times (RTs) and anxiety levels were measured. We compared RTs to a pleasant and an unpleasant food odor between high- and low-trait anxiety participants. We found that high-trait anxiety participants detected both odors faster than low-trait anxiety participants, independently of odor pleasantness. Moreover, trait anxiety levels significantly correlated with reaction times to both odors, indicating that trait anxiety but not odor pleasantness influences olfactory detection speed. These findings provide new insights into olfactory processing in healthy adults showing how various levels of trait anxiety affect the olfactory modality.

Olfactory perception is positively linked to anxiety in young adults

Olfactory abilities show a high degree of inter-individual variability and this could be partly related to personality differences. Here, in two studies, we tested a potential link between personality dimensions and olfactory perception. Sixty-eight (study 1) and a hundred and fifty-six (study 2) young adults completed the Big Five questionnaire and performed the Sniffin' Sticks test for assessing odour threshold, identification, and (in study 2) discrimination. In neither study did we find a significant link between personality dimensions and olfactory identification scores. However, in study 1, we found a significant positive correlation between the neuroticism dimension and olfactory sensitivity. This was mainly due to the anxiety and self-consciousness subscales, which load onto the neuroticism dimension. In a follow-up study, we again found a significant association between anxiety and odour perception, specifically in odour discrimination. Our results indicate that variability in anxiety could partly explain the high inter-individual variation in olfactory perception.