Multiple chemical sensitivity: on the scent of central sensitization

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.

Neurological susceptibility to environmental exposures: pathophysiological mechanisms in neurodegeneration and multiple chemical sensitivity

The World Health Organization lists air pollution as one of the top five risks for developing chronic non-communicable disease, joining tobacco use, harmful use of alcohol, unhealthy diets and physical inactivity. This review focuses on how host defense mechanisms against adverse airborne exposures relate to the probable interacting and overlapping pathophysiological features of neurodegeneration and multiple chemical sensitivity. Significant long-term airborne exposures can contribute to oxidative stress, systemic inflammation, transient receptor subfamily vanilloid 1 (TRPV1) and subfamily ankyrin 1 (TRPA1) upregulation and sensitization, with impacts on olfactory and trigeminal nerve function, and eventual loss of brain mass. The potential for neurologic dysfunction, including decreased cognition, chronic pain and central sensitization related to airborne contaminants, can be magnified by genetic polymorphisms that result in less effective detoxification. Onset of neurodegenerative disorders is subtle, with early loss of brain mass and loss of sense of smell. Onset of MCS may be gradual following long-term low dose airborne exposures, or acute following a recognizable exposure. Upregulation of chemosensitive TRPV1 and TRPA1 polymodal receptors has been observed in patients with neurodegeneration, and chemically sensitive individuals with asthma, migraine and MCS. In people with chemical sensitivity, these receptors are also sensitized, which is defined as a reduction in the threshold and an increase in the magnitude of a response to noxious stimulation. There is likely damage to the olfactory system in neurodegeneration and trigeminal nerve hypersensitivity in MCS, with different effects on olfactory processing. The associations of low vitamin D levels and protein kinase activity seen in neurodegeneration have not been studied in MCS. Table 2 presents a summary of neurodegeneration and MCS, comparing 16 distinctive genetic, pathophysiological and clinical features associated with air pollution exposures. There is significant overlap, suggesting potential comorbidity. Canadian Health Measures Survey data indicates an overlap between neurodegeneration and MCS (p < 0.05) that suggests comorbidity, but the extent of increased susceptibility to the other condition is not established. Nevertheless, the pathways to the development of these conditions likely involve TRPV1 and TRPA1 receptors, and so it is hypothesized that manifestation of neurodegeneration and/or MCS and possibly why there is divergence may be influenced by polymorphisms of these receptors, among other factors.

Multiple Chemical Sensitivity Syndrome: First Symptoms and Evolution of the Clinical Picture: Case-Control Study/Epidemiological Case-Control Study

Multiple chemical sensitivity (MCS) is a chronic condition characterized by the appearance of symptoms caused by exposure to chemical compounds that are tolerable for the general population. It mainly affects middle-aged women. There are very few studies focusing on the most frequent symptoms of MCS considering age groups and gender. The main goal of this study was to find the most frequent symptoms both at the onset of the disease and at the present time describing them by age groups. The QEESI (Quick Environmental Exposure and Sensitivity Inventory) questionnaire, Scale 3 which assesses symptoms and their severity, was used as a diagnostic tool for the disease. A case-control study was conducted with the participation of 210 people. Of the cases, 94.3% were women. The symptoms that most often manifested first were airway and mucous membrane alterations (68.9%). In the development of the disease, we found cognitive alterations (OR = 31.25), heart or chest problems (OR = 22.49), neuromuscular problems (OR = 20.00) and head-related symptomatology (OR = 19.29). Identifying the most frequent pattern of symptoms by age group and sex will allow an early diagnosis of the disease to improve its prognosis and treatment.

Potential factors affecting chronic chemical intolerance associated with constitutional predisposition or lifestyle and environment during childhood: From a six-year follow-up study

OBJECTIVE

The Japanese chemical intolerance (JCI) study was conducted in January 2012 with a cohort of 7245 adults from population-based sampling. This study aimed to investigate the childhood constitutional and environmental factors involved in the development of chronic CI from the prospective cohort study.

METHODS

In the cohort, 4683 persons were identified after six years. Self-reported questionnaires were administered to the subjects to obtain information on CI status; medical history; constitution, lifestyle, and housing environment during childhood; and recent psychosomatic states. We assessed the differences between individuals with persisting CI status during the follow-up (defined as chronic CI) and controls not having CI status during the follow-up.

RESULTS

A total of 2500 individuals responded. Multiple logistic regression analyses revealed significant associations between chronic CI and motion sickness to car or bus and allergic conjunctivitis during childhood. Significant associations between a possible increased risk of CI and the existence of high-voltage power lines close to housing, the use of vinyl covering in wall material, the use of strong perfume by a family member, and the experience of stinky odor of paint or wax at elementary school were observed. However, the use of carpet in floor material and plaster coating in wall material was associated with a possible decreased risk of CI.

CONCLUSIONS

Some potential constitutional predisposition from childhood, including inherent susceptibility in the autonomic nervous system may be involved in the development of CI.

Conditioned pain modulation and pain sensitivity in functional somatic disorders: The DanFunD study

Background

Disrupted pain regulation has been proposed as a component in functional somatic disorders (FSD). The objective of this study was to examine a general population sample, encompassing three delimitations of FSD while assessing pain sensitivity and conditioning pain modulation (CPM).

Methods

Pressure pain thresholds (PPTs) at the tibialis and trapezius muscles were recorded at baseline. During cold pressor stimulation of the hand, the tibialis PPTs were re‐assessed and the difference from baseline measures defined the CPM effect. Participants (n = 2,198, 53% females) were randomly selected from the adult Danish population. FSD was established by self‐reported symptom questionnaires.

Results

With a few exceptions, only weak associations were seen between PPTs and CPM in cases with FSD (p > .1). A high PPT was associated with lower odds of having multi‐organ bodily distress syndrome (OR^{PPT trapezius}: 0.66, 95% CI: 0.49–0.88, p = .005), with the symptom profile characterized by all symptoms (OR^{PPT trapezius}: 0.72, 95% CI: 0.58–0.90, p = .003 and OR^{PPT tibialis}: 0.75, 95% CI: 0.62–0.91, p = .004), and with multiple chemical sensitivity (OR^{PPT trapezius}: 0.81, 95% CI: 0.67–0.97, p = .022). High CPM was associated with high odds of having irritable bowel (OR^{CPM relative}: 1.22, 95% CI: 1.04–1.43, p = .013 and OR^{CPM absolute} = 2.66, 95% CI: 1.07–6.45, p = .033).

Conclusion

However, only PPT measured over the trapezius muscle were still significant after correction for multiple testing for the symptom profile characterized by all symptoms. Findings from this study do not support altered pain regulation in questionnaire‐based FSD which is in contrast with the existing presumption. Further epidemiological studies in this field are needed.

Significance

Disrupted pain regulation as measured by abnormal pain thresholds has been hypothesized as a central mechanism in Functional Somatic Disorders (FSD). The hypothesis has been raised in clinical setting where patients presented subjective and objective features of hypersensitivity. The present population‐based study does not support this notion. This points to the importance of further studies into the underlying pathophysiology mechanisms of FSD.

Pain Perception, Brain Connectivity, and Neurochemistry in Healthy, Capsaicin-Sensitive Subjects

Most of the occupational exposure limits (OELs) are based on local irritants. However, exposure to much lower concentrations of irritant substances can also lead to health complaints from workers. Exposure to irritants is often accompanied by strong unpleasant odors, and strong odors might have distracting effects and hence pose a safety risk. The findings obtained in human exposure studies with chemically sensitive, stressed, or anxious persons suggest that their ability to direct attention away from the odorous exposure and to focus on a cognitive task is reduced. In addition, after repeated odor exposure, these persons show signs of sensitization, i.e., difficulties in ignoring or getting used to the exposure. The question arises as to whether certain health conditions are accompanied by a change in sensitivity to odors and irritants, so that these persons are potentially more distracted by odors and irritants and therefore more challenged in working memory tasks than nonsusceptible persons. In our study, susceptible persons with sensory airway hyperreactivity ("capsaicin-sensitive") respond more strongly to mechanical skin stimuli than controls and show altered network connectivity. Capsaicin-sensitive subjects have a lower pain threshold and thus are more sensitive to mechanical skin stimuli. The intrinsic functional connectivity of their saliency network is higher, and the lower the GABAergic tone of the thalamus, the higher their pain sensitivity to mechanical stimuli. It seems that the increased communication between resting-state networks promotes a stronger perception of the sensory input signal. The results can be used to inform about actual risks (i.e., attention diversion and increased risk of accidents) and "pseudo" risks such as odor perception without a negative impact on one's well-being. This way, uncertainties that still prevail in the health assessment of odorous and sensory irritating chemicals could be reduced.

DNA damage and inflammatory response in workers exposed to fuels and paints

Workers exposed to fuels and paints may present alterations in several parameters. Thus, we assessed potential biomarkers, with the aim of detecting early changes in gasoline station attendants and painters. Blood samples were collected for the analysis of inflammatory and DNA damage markers, besides biochemical, haematological and oxidative stress parameters. Biochemical and haematological parameters, which are assessed with routine exams, showed few changes. However, these findings could mask the workers' real health status. Besides, markers of oxidative damage were not modified. Levels of inflammatory parameters (cytokines and nitric oxide levels) and the DNA damage marker 8-hydroxydeoxyguanosine were significantly changed in the workers. Our results suggest that inflammatory and DNA damage parameters can be potential biomarkers for the biological monitoring of workers exposed to fuels and paints and may contribute to the development of occupational protection standards.

Chemical intolerance: involvement of brain function and networks after exposure to extrinsic stimuli perceived as hazardous

Background

Chemical intolerance (CI) is a chronic condition characterized by recurring and severe symptoms triggered by exposure to low levels of odorous or pungent substances. The etiology of CI has been a controversial subject for a long time. The aim of this review is to summarize findings on the neurological processing of sensory information during and after exposure to low levels of odorous or pungent substances in individuals with CI, focusing on the brain function and networks.

Methods

Scientific studies on CI published between 2000 and 2019 in academic peer-reviewed journals were systematically searched using medical and scientific literature databases. Only peer-reviewed articles reporting original research from experimental human studies directly associated with CI, and involving related neurological responses or brain imaging after exposure to odorous or pungent substances (i.e., in chemical provocation tests), were considered.

Results

Forty-seven studies were found to be eligible for a full-text review. Twenty-three studies met the selection criteria and were included in this review. Evidence indicated that differences between subjects with CI and healthy controls were observed by brain imaging during and after exposure to odorous or pungent substances. Differences in brain imaging were also observed between initial exposure and after exposure to these substances. Neurological processing of sensory information after exposure to extrinsic stimuli in the limbic system and related cortices were altered in subjects with CI. A previous documentable exposure event was likely to be involved in this alteration.

Conclusions

This review documents consistent evidence for the altered neurological processing of sensory information in individuals with CI. Further neurophysiological research exploring the processing of extrinsic stimuli and cognition of sensation through the limbic system and related cortices in CI, and the appearance of symptoms in individuals with CI, are required.

How do women suffering from multiple chemical sensitivity experience the medical encounter? a qualitative study in Spain

PURPOSE

Multiple Chemical Sensitivity is a condition principally suffered by women. As with fibromyalgia and chronic fatigue syndrome, Multiple Chemical Sensitivity is usually included among the so called "contested illnesses", defined as illnesses whose cause, diagnosis, prevalence and even existence are subject to controversy. This article seeks to explore how women with Multiple Chemical Sensitivity experience this contested illness, through their own descriptions of diagnostic processes, search for treatment and encounters with different health professionals. We aim to observe these experiences in detail and to identify aspects that could improve care for Multiple Chemical Sensitivity sufferers.

METHOD

Qualitative design. We performed personal in-depth interviews, which were recorded and transcribed to conduct a qualitative content analysis supported by Atlas.ti-7.

SUBJECTS/PATIENTS

22 women diagnosed with Multiple Chemical Sensitivity in Spain.

RESULTS

Two main categories were identified in the interviews: (1) unavoidable barriers: patients' exposure to chemicals and the absence of treatment, and (2) Skepticism on the part of care providers and lack of recognition in the process of diagnosis.

CONCLUSION

Training and above all awareness raising strategies are needed to address health professionals' prejudices regarding the existence of contested illnesses such as Multiple Chemical Sensitivity. These prejudices hinder diagnosis and medical follow-up, and add negative emotions to the physical limitations already suffered by patients.IMPLICATIONS FOR REHABILITATION Multiple Chemical SensitivityIt is important to promote a compassionate and empathetic attitude among health providers, in order to avoid rejection and delegitimization of the experiences of women with Multiple Chemical Sensitivity.Multiple Chemical Sensitivity protocols should be developed and implemented to give skills to health professionals to assist patients with Multiple Chemical Sensitivity.These protocols should include avoidance of exposure to chemicals present in healthcare facilities.Training programs for health providers should include not only knowledge, but awareness raising about the characteristics and severity of contested illnesses such as Multiple Chemical Sensitivity.Health providers should avoid stigmatizing patients by psychologizing their symptoms and be aware of the existence of stereotypes regarding women suffering from Multiple Chemical Sensitivity.

Exploratory Investigation of a Brief Cognitive Behavioral Intervention and Transcranial Direct Current Stimulation on Odor Sensitivity

OBJECTIVE

Enhanced odor sensitivity is a phenomenon that potentially underlies conditions such as multiple chemical sensitivity (MCS). Currently, there are no treatments that have been shown to effectively decrease odor sensitivity. Given similarities of odor hypersensitivity/MCS to pain sensitization disorders such as fibromyalgia, there may be a potential for interventions that improve pain tolerance to modulate odor sensitivity.

METHODS

This exploratory study randomized 72 healthy community adult volunteers to receive one of six treatments in between two assessments of thermal pain tolerance and odor threshold. Participants were randomized to receive either cathodal, anodal, or sham transcranial direct current stimulation (tDCS) aimed at dorsolateral prefrontal cortex. In addition, participants were provided a brief cognitive behavioral intervention (CBI) for pain consisting of task framing, cognitive restructuring, and distraction technique training, or a control intervention consisting of information about pain.

RESULTS

Persons who received a brief CBI showed significantly increased odor thresholds (reduced sensitivity) during intervention (F (1,62) = 7.29, p = .009, ηp = .11), whereas the control intervention was not associated with altered odor thresholds. Moreover, in those who received brief CBI, more severe anxiety associated with larger reductions in odor sensitivity (ρ = .364, p = .035). There was no effect of tDCS (F (2,62) = .11, p = .90) nor interaction between tDCS and CBI (F (2,62) = .32, p = .73).

CONCLUSIONS

Given the connection between anxiety and MCS, results suggest that CBT techniques for somatic processes may show promise in treating conditions characterized by increased sensitivity to odors (e.g., MCS).

Factors affecting self-reported chemical intolerance: A five-year follow-up study in Japan

OBJECTIVE

Chemical intolerance (CI) has become a strong public health concern in industrialized countries. The Japanese Chemical Intolerance (JCI) study was conducted in January 2012 with a cohort of 7245 adults from population-based sampling as the baseline. The aim of the present study was to investigate the factors involved in the improvement and development of CI from the five-year follow-up study.

METHODS

From the 7245 cohort, 735 persons with CI (case) were identified, and 1750 controls without CI were randomly selected to match gender and age for case and control groups. Self-reported questionnaires were administered to the subjects of the two groups to obtain information on status of CI; medical history; medical, lifestyle, or physical interventions; changes in living situation or occupation; and psychosomatic states.

RESULTS

A total of 909 individuals responded during the follow-up period. After five years, improvement in CI was observed in 67.7% of the case group. Status of CI was reported in 6.7% of the control group. Multiple logistic regression analyses revealed that baseline atopic dermatitis and negative psychosomatic states including irritability, fatigue, anxiety, depressed mood, and somatic symptoms were significantly associated with development of CI in controls. Appropriate physical activity and maintaining a regular lifestyle including diet or sleep during the last three years of the follow-up period were significant factors for improvement of CI in the case group.

CONCLUSIONS

Ensuring appropriate physical activity and regular lifestyle rather than improving physical environment lead to improvement of CI. Stable psychosomatic state is essential for preventing CI.

Central sensitization in chronic pain and medically unexplained symptom research: A systematic review of definitions, operationalizations and measurement instruments

OBJECTIVE

Central sensitization (CS), a mechanism explaining the persistence of symptoms, has been the focus of many research projects. Explanations given to patients with chronic pain are often based on this mechanism. It is hypothesized that CS also plays an important role in the persistence of medically unexplained symptoms (MUS). However, definitions and operationalizations of CS vary. We conducted a systematic review of definitions, operationalizations and measurement instruments of CS.

METHODS

We searched in PubMed, EMBASE, PsycINFO, Cinahl and The Cochrane Library till September 2017 and included papers that addressed CS in relation to chronic pain and/or MUS. Two reviewers independently selected, analysed and classified information from the selected publications. We performed a thematic analysis of definitions and operationalizations. We listed the measurement instruments.

RESULTS

We included 126 publications, 79 publications concerned chronic pain, 47 publications concerned MUS. Definitions of CS consistently encompass the theme hyperexcitability of the central nervous system (CNS). Additional themes are variably present: CNS locations, nature of sensory input, reduced inhibition and activation and modulation of the NDMA receptor. Hyperalgesia and allodynia are widely mentioned as operationalizations of CS. Quantitative sensory testing (QST) and (f)MRI are the most reported measurement instruments.

CONCLUSIONS

There is consensus that hyperexcitability is the central mechanism of CS. Operationalizations are based on this mechanism and additional components. There are many measurement instruments available, whose clinical value has still to be determined. There were no systematic differences in definitions and operationalizations between the publications addressing MUS and those addressing chronic pain.

Epidemiological association between multiple chemical sensitivity and birth by caesarean section: a nationwide case-control study

INTRODUCTION

Multiple chemical sensitivity (MCS) is characterized by recurrent nonspecific symptoms that are attributed to exposure to trace levels of environmental agents. Although the clinical symptoms of MCS have been described in several studies, the risk factors for this condition remain unclear. Our aim was to clarify the risk factors for MCS and the association between MCS and birth by caesarean section.

METHODS

We conducted a nationwide case-control study of Japanese individuals (aged 20-65 years) with physician-diagnosed MCS (183 cases) and without MCS (345 controls). The study participants were selected from among 150,000 people in a web-based research panel with approximately 1,000,000 registrants. They completed an online survey including questions on their sociodemographic characteristics, birth history (i.e., birth by caesarean section), and other potential risk factors for MCS. Multivariate logistic regression analysis was employed to determine the association between sociodemographic characteristics and the risk of MCS.

RESULTS

The proportions of case and control subjects who were born by caesarean section were 39.9 and 7.0%, respectively. The association between birth by caesarean section and MCS was significant even after adjusting for potential confounders (adjusted odds ratio: 6.15; 95% confidence interval: 3.13-12.1). A history of agricultural work, mouth breathing, ≥11 vaccinations in the past 10 years, and residing in a new home (< 1 year-old) ≥3 times were also significantly associated with MCS.

CONCLUSION

Our data indicate an epidemiological link between MCS and birth by caesarean section. Moreover, we show that factors other than chemical exposure may be associated with the development of MCS.

Background factors of chemical intolerance and parent-child relationships

Background

Chemical intolerance is a widespread public health problem characterized by symptoms that reportedly result from low-level exposure to chemicals. Although several studies have reported factors related to chemical intolerance in adults, the impact of family members has not been reported. In the present study, we investigated the background factors related to chemical intolerance in family members and parent–child relationships.

Methods

We distributed a self-reported questionnaire to 4325 mothers who were invited to visit the Kishiwada Health Center in Kishiwada City, Osaka, between January 2006 and December 2007 for the regular health checkup of their three-and-a-half-year-old children.

Results

The prevalence of chemical intolerance in the 3-year-old children was almost one eighteenth of that reported by their mothers. Multiple logistic regression analyses revealed that cold sensitivity [odds ratio (OR), 1.89; 95% confidence interval (CI), 1.04–3.44], past bronchial asthma (OR, 2.84; 95% CI, 1.46–5.53), and any past allergies (OR, 2.21; 95% CI, 1.36–3.60) were significantly associated with chemical intolerance in the mother. The presence of indoor cat during childhood (OR, 1.99; 95% CI, 1.08–3.69) was significantly associated with chemical intolerance in the mother; however, the association was weak compared with cold sensitivity and past asthma and allergies. The current chemical intolerance of the mother was significantly associated with allergic rhinitis (OR, 2.32; 95% CI, 1.19–4.53), bronchial asthma (OR, 3.66; 95% CI, 2.00–6.69), and chronic bronchitis (OR, 3.69; 95% CI, 1.04–13.03) in her 3-year-old child.

Conclusions

The results suggest that inherent physical constitution and childhood housing environment are associated with a risk of acquiring chemical intolerance. Children of mothers with chemical intolerance have a possible risk of respiratory hypersensitivity or inflammation. Further investigation is recommended to determine the inherent physical constitution and background environmental factors associated with the risk of acquiring chemical intolerance. The impact of having mothers with chemical intolerance on the health of children also requires further study.

Electronic supplementary material

The online version of this article (10.1186/s12199-018-0743-y) contains supplementary material, which is available to authorized users.

A randomised, placebo-controlled trial of transcranial pulsed electromagnetic fields in patients with multiple chemical sensitivity

OBJECTIVE

To evaluate the efficacy of transcranially applied pulsed electromagnetic fields (PEMF) on functional impairments and symptom severity in multiple chemical sensitivity (MCS) patients.

METHODS

The study was conducted as a nationwide trial in Denmark using a randomised, parallel-group, double-blind and placebo-controlled design. Sample size was estimated at 40 participants. Eligibility criteria were age 18-75 years and fulfilment of the MCS case criteria. Participants received either PEMF or placebo PEMF (no stimulation) applied transcranially for 6 weeks. The primary outcome was the Life Impact Scale (LIS) of the Quick Environmental Exposure and Sensitivity Inventory (QEESI). Secondary outcomes were the Symptom Severity Scale (SSS) and the Chemical Intolerance Scale of QEESI.

RESULTS

A total of 39 participants were randomised to PEMF or placebo treatment. No significant difference was observed on QEESI LIS between groups with a mean change score of -5.9 in the PEMF group compared with -1.5 in the placebo group (p=0.35, effect size=-0.31). However, a significant decrease was detected on QEESI SSS within and between groups with a mean change score of -11.3 in the PEMF group compared with -3.2 in the placebo group (p=0.03, effect size=-0.60).

CONCLUSION

PEMF treatment of 6 weeks showed no effect on functional impairments in MCS. However, a significant decrease in symptom severity was observed.

Symptoms from masked acrolein exposure suggest altered trigeminal reactivity in chemical intolerance

BACKGROUND

Chemical intolerance (CI) is a widespread occupational and public health problem characterized by symptoms that reportedly result from low-levels of chemical exposure. The mechanisms behind CI are unknown, however modifications of the chemical senses (rather than toxic processes) have been suggested as key components. The aim of this study was to investigate whether individuals with self-reported CI report more sensory irritation during masked acrolein exposure compared to controls without CI.

METHODS

Individuals with CI (n=18) and controls without CI (n=19) were exposed in an exposure chamber. Each participant took part in two exposure conditions - one with heptane (the masking compound), and one with heptane and acrolein at a dose below previously reported sensory irritation thresholds. The exposures lasted for 60min. Symptoms and confidence ratings were measured continuously throughout the exposure as were measurements of electrodermal activity and self-reported tear-film break-up time. Participants were blind to exposure condition.

RESULTS

Individuals with CI, compared with controls reported greater sensory irritation in the eyes, nose and throat when exposed to acrolein masked with heptane. There was no difference during exposure to heptane.

CONCLUSIONS

Masked exposure to acrolein at a concentration below the previously reported detection threshold is perceived as more irritating by individuals with CI compared with controls. The results indicate that there is altered trigeminal reactivity in those with CI compared to controls.

Intolerance to environmental chemicals and sounds in irritable bowel syndrome: Explained by central sensitization?

This study tested the hypotheses of irritable bowel syndrome showing (1) comorbidity with chemical and sound intolerance, other types of functionally somatic syndromes, and psychiatric disorders and (2) stronger than normal affective reactions to and behavioral disruptions from odorous/pungent chemicals and sounds in daily life. These hypotheses were tested by means of data from a large-scale population-based questionnaire study. The results showed comorbidity in irritable bowel syndrome with chemical and sound intolerance, fibromyalgia, migraine, post-traumatic stress disorder, generalized anxiety disorder, panic syndrome, and depression as well as strong reactions/disruptions from odorous/pungent chemicals and sounds in irritable bowel syndrome.

Mindfulness-based cognitive therapy (MBCT) for multiple chemical sensitivity (MCS): Results from a randomized controlled trial with 1 year follow-up

OBJECTIVE

Multiple chemical sensitivity (MCS) is a medically unexplained condition characterized by symptoms from multiple organ systems following the perception of common odorants. The condition can cause severe functional impairment for afflicted individuals. The aim of this study was to assess the effects of mindfulness-based cognitive therapy (MBCT) for individuals with MCS.

METHODS

The intention-to-treat sample (ITT) included 69 individuals who had been randomized to either MBCT or treatment as usual (TAU). The primary outcome measure was the Quick Environmental Exposure and Sensitivity Inventory (QEESI), which measures the following aspects of

MCS

impact of MCS on daily life, symptoms, and reactions following chemical exposures. Secondary outcome measures included the Brief Illness Perception Questionnaire (BIPQ) and the anxiety and depression subscales of the symptom checklist 92 (SCL-92). Participants were assessed at baseline and post treatment, and at follow-up periods of 6- and 12-months.

RESULTS

We found no effect of MBCT on the primary outcome, nor did we find an effect on levels of depression or anxiety. We did, however, find positive changes in illness perceptions, which were sustained at 12-month follow-up. Dropout rates were low, suggesting MBCT was well received and regarded as an acceptable intervention by individuals with MCS.

CONCLUSIONS

Overall, these results suggest that MBCT does not change overall illness status in individuals with MCS, but that MBCT positively changes emotional and cognitive representations. Possible explanations for these results are discussed.

Negative affect is associated with development and persistence of chemical intolerance: a prospective population-based study

OBJECTIVE

Chemical intolerance (CI) is characterised by negative health effects attributed to a heightened responsiveness to common airborne chemicals. This longitudinal study explored the hypothesised role of negative affect in the development and persistence of CI in a general population.

METHODS

A general population sample aged 19 to 72 years was examined in 2006-2008 and again in 2011-2012. Longitudinal data on CI were analysed with the purpose of examining baseline negative affect as a risk factor for having developed CI at 5-year follow-up and for reporting persistent CI. Participants were classified as reporting no signs of CI, having symptoms of CI and as being a likely CI case based on self-reported reactions to 11 common chemical exposures, symptoms related to chemical exposures and daily life adjustments attributed to reactions when exposed to chemicals.

RESULTS

A total of 69.4% of the participants who had reported CI at baseline also reported CI at follow-up. In participants with no baseline CI, 15.5% reported CI at follow-up and 18.1% reported symptoms related to chemicals but no daily life adjustments. Baseline negative affect was positively and statistically significantly associated with both development and persistence of CI.

CONCLUSIONS

Initial reports of CI were found to be persistent over time, and a considerable proportion of the participants with no CI at baseline reported having developed CI after 5 years. The positive association between negative affect and CI at the 5-year follow-up supports negative affect as a possible risk factor for CI.

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.

Two of three patients with multiple chemical sensitivity had less symptoms and secondary hyperalgesia after transcranially applied pulsed electromagnetic fields

Background Multiple chemical sensitivity (MCS) is a chronic, disabling condition characterized by recurrent multisystem symptoms triggered by common airborne chemicals. Evidence points towards abnormal sensory processing in the central nervous system (CNS) as a likely pathophysiological mechanism. No effective treatment has yet been reported, but clinical observations suggest that as pulsed electromagnetic fields (PEMF) is a treatment for some CNS disorders (depression and chronic pain), it may also be a treatment modality for MCS. Methods In an open case study, the effects of PEMF were assessed in three MCS patients. All cases received 30 min daily treatment 5 days a week for 8 consecutive weeks. Symptoms and functional impairments related to MCS, depressive symptoms, and capsaicin-induced secondary punctate hyperalgesia were assessed at baseline and weekly until an 18-week follow-up. Results Two of the three cases showed considerable improvement on all measures of symptoms and functional impairments related to MCS in response to PEMF therapy. One case showed no improvement and during the treatment period was unexpectedly diagnosed with depression. Conclusion Our findings indicate potential benefits of PEMF therapy in MCS. Implication The therapeutic effect of PEMF in MCS needs to be investigated by a randomized placebo-controlled trial.

Transcranial pulsed electromagnetic fields for multiple chemical sensitivity: study protocol for a randomized, double-blind, placebo-controlled trial

Background

Multiple chemical sensitivity (MCS) is a chronic condition of unknown etiology. MCS is characterized by recurrent nonspecific symptoms from multiple organ systems in response to chemical exposures in concentrations that are normally tolerated by the majority of the population. The symptoms may have severe impact on patients’ lives, but an evidence-based treatment for the condition is nonexisting. The pathophysiology is unclarified, but several indicators point towards abnormal processing of sensory signals in the central nervous system. Pulsed electromagnetic fields (PEMF) offer a promising new treatment for refractory depression and can be targeted at the brain, thereby activating biochemical cell processes.

Methods/Design

In a parallel, randomized, double-blind, placebo-controlled trial conducted at the Danish Research Centre for Chemical Sensitivities, the effects of PEMF in MCS patients will be assessed using the Re5 Independent System. Based on sample size estimation, 40 participants will be randomized to either PEMF therapy or placebo. The allocation sequence will be generated by computer. All involved parties (that is, participants, investigators, the research nurse, and the statistician) will be blinded to group allocation. The participants will receive PEMF therapy or placebo applied transcranially 30 minutes twice a day for 7 days a week over 6 consecutive weeks. Outcomes will be measured at baseline, once weekly during treatment, post treatment, and at 2.5-month and 4.5-month follow-up according to a predefined timetable. The primary outcome will be a measurement of the impact of MCS on everyday life. The secondary outcomes will be measurements of MCS symptoms, psychological distress (stress, anxiety or depressive symptoms), capsaicin-induced secondary punctate hyperalgesia, immunological markers in serum, and quality of life.

Discussion

This trial will assess the effects of PEMF therapy for MCS. Currently, there is no treatment with a documented effect on MCS, and in terms of healthcare there is very little to offer these patients. There is thus a great need for well-conducted randomized trials aimed at assessing possible treatment effects. A positive outcome will pave the way for improved healthcare and understanding of this very disabling and overlooked condition.

Trial registration

ClinicalTrials.gov, NCT01834781

[Etiopathogenetic aspects of somatoform disorders]

The etiopathology of somatoform disorders can only be understood against the background of an integrated biopsychosocial model. Cultural and historical influences must be taken into account as well as contemporary settings of scientific or medical priorities. In this context the emphasis on neurobiological findings can be interpreted as the non-accidental struggle for legitimacy of both patients and physicians. Altogether the available data on factors influencing the formation and maintenance of somatoform symptoms has to be described as both diverse and unspecific and thus points to a challenging research program in the coming years.