Neural sensitization model for multiple chemical sensitivity: overview of theory and empirical evidence

Consumption of Energy Drinks among Italian University students: a cross-sectional multicenter study

PURPOSE

The aim of the study was to evaluate the caffeinated Energy Drinks (EDs) consumption among a large sample of Italian undergraduates and its association with some of the major lifestyle risk factors.

METHODS

Students attending twelve public Italian universities were involved between October 2021 and May 2022. Information on socio-demographic characteristics, ED consumption, and on health-related behaviors of participants was collected by the use of a web-based questionnaire.

RESULTS

A total of 2165 students participated in the study and 15.2% of them reported having used caffeinated EDs in the last six months, mainly once a month (41.5%). In comparison with non-users, ED users showed a higher proportion of males (p < 0.001) and a higher father's educational level (p = 0.003), came mainly from Northern universities (p = 0.004) and life sciences degree courses (p < 0.001). Besides, ED users reported higher BMI values (p = 0.003), more particular dietary regimens (p < 0.001), higher levels of weekly moderate-vigorous physical activity (p < 0.001) and participation in sports (p < 0.001) and in team sports (p = 0.003), and higher proportion of smokers (p < 0.001) and alcohol drinkers (p = 0.005). ED use was negatively related with female gender (OR 0.546; 95% CI 0.374-0.798), the Mediterranean diet (OR 0.587; 95% CI 0.362-0.951) and coming from the center of Italy (OR 0.500; 95% CI 0.275-0.909) and positively associated with tobacco smoke (OR 1.712; 95% CI 1.176-2.492) and participation in a team sport (OR 1.686; 95% CI 1.051-2.707).

CONCLUSION

These findings could encourage figures engaged in education to increase the students' awareness on this issue in order to prevent the excessive use of EDs and associated unhealthy behaviors, especially in the most interested subgroups.

PON1 polymorphisms can predict generalized anxiety and depressed mood in patients with multiple chemical sensitivity

Background: Multiple chemical sensitivity (MCS) is a chronic condition with somatic, cognitive and affective symptoms that follow contact with chemical agents at usually non toxic concentrations. We aimed to assess the role of genetic polymorphisms involved in oxidative stress on anxiety and depression in MCS. Materials & methods: Our study investigated the CAT rs1001179, MPO rs2333227, PON1 rs662 and PON1 rs705379 polymorphisms in MCS. Results: The AG genotype of the PON1 rs662 and the TT and CT genotypes of the PON1 rs705379 were involved in anxiety and depression. Discussion: These results are in line with existing evidence of PON1 involvement in MCS and suggest a further role of this gene in the exhibition of anxiety and depression in this disease.

What I have learnt from helping thousands of people taper off antidepressants and other psychotropic medications

Although psychiatric drug withdrawal syndromes have been recognized since the 1950s - recent studies confirm antidepressant withdrawal syndrome incidence upwards of 40% - medical information about how to safely go off the drugs has been lacking. To fill this gap, over the last 25 years, patients have developed a robust Internet-based subculture of peer support for tapering off psychiatric drugs and recovering from withdrawal syndrome. This account from the founder of such an online community covers lessons learned from thousands of patients regarding common experiences with medical providers, identification of adverse drug reactions, risk factors for withdrawal, tapering techniques, withdrawal symptoms, protracted withdrawal syndrome, and strategies to cope with symptoms, in the context of the existing scientific literature.

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.

Prototype stories of life with Chemical Intolerance – when the environment becomes a threat to health and well-being

We aimed to explore how individuals living with Chemical Intolerance (CI) describe the onset and progression of CI, and how they live and cope with CI. The participants were recruited via Swedish websites hosted by CI support groups. A postal survey, including a Life history calender, was sent to potential participants. Eleven respondents fitted the consensus-based criteria for CI while not reporting comorbidity. A narrative analysis of their written replies resulted in five prototypical stories based on similarities in the onset and course of CI. All five stories contain descriptions of alienation from society and insufficient social support. Differences in participants’ perceptions of the symptom onset – with regard to suddenness, the point in life and the perceived cause of symptoms – partly corresponded to etiological theories of CI related to stress or inflammation. Further differences between the prototype stories mainly concern the possible effects on health and well-being related to social support and coping. Given these differences, we recommend that medical professionals and others apply a holistic, context-sensitive approach before discouraging or promoting a specific coping strategy in relation to CI.

Severe Adverse Reactions Following Ketoconazole, Fluconazole, and Environmental Exposures: A Case Report

In this case report, we describe a 66-year-old man who developed multiple adverse reactions beginning at age 56 after exposure to several azole antifungal drugs including ketoconazole and fluconazole. He also had a history of more than 40 years exposure to chemicals including pesticides, wood preservatives, fertilizers, and welding chemicals. His reactions involved dehydration (requiring several liters of intravenous fluids in less than an hour to alleviate this condition), angioedema, nausea, tinnitus, hypotension, and difficulty breathing. His acute adverse reactions were triggered by a wide range of chemicals including gasoline, diesel fuel, pesticides, chlorine, topical isopropyl alcohol, and paper mill emissions. His acute reactions were also triggered by a wide range of foods such as bananas, apples, milk, white potatoes, and processed sweets. A number of mechanisms could be responsible for his increased sensitivity to chemicals following exposure to fluconazole/ketoconazole, including inhibition of P450 and other detoxification enzymes, acetaldehyde buildup, and neurogenic sensitization.

Gene expression profiling in persons with multiple chemical sensitivity before and after a controlled n-butanol exposure session

OBJECTIVES

To investigate the pathophysiological pathways leading to symptoms elicitation in multiple chemical sensitivity (MCS) by comparing gene expression in MCS participants and healthy controls before and after a chemical exposure optimised to cause symptoms among MCS participants.The first hypothesis was that unexposed and symptom-free MCS participants have similar gene expression patterns to controls and a second hypothesis that MCS participants can be separated from controls based on differential gene expression upon a controlled n-butanol exposure.

DESIGN

Participants were exposed to 3.7 ppm n-butanol while seated in a windowed exposure chamber for 60 min. A total of 26 genes involved in biochemical pathways found in the literature have been proposed to play a role in the pathogenesis of MCS and other functional somatic syndromes were selected. Expression levels were compared between MCS and controls before, within 15 min after being exposed to and 4 hours after the exposure.

SETTINGS

Participants suffering from MCS and healthy controls were recruited through advertisement at public places and in a local newspaper.

PARTICIPANTS

36 participants who considered themselves sensitive were prescreened for eligibility. 18 sensitive persons fulfilling the criteria for MCS were enrolled together with 18 healthy controls.

OUTCOME MEASURES

17 genes showed sufficient transcriptional level for analysis. Group comparisons were conducted for each gene at the 3 times points and for the computed area under the curve (AUC) expression levels.

RESULTS

MCS participants and controls displayed similar gene expression levels both at baseline and after the exposure and the computed AUC values were likewise comparable between the 2 groups. The intragroup variation in expression levels among MCS participants was noticeably greater than the controls.

CONCLUSIONS

MCS participants and controls have similar gene expression levels at baseline and it was not possible to separate MCS participants from controls based on gene expression measured after the exposure.

Application of Quick Environment Exposure Sensitivity Inventory (QEESI©) for Japanese population: study of reliability and validity of the questionnaire

A standardized questionnaire has not been established for screening or diagnostic assessment of patients with multiple chemical sensitivity (MCS) in Japan. In the US, Miller and Prihoda (1999a, b) developed a questionnaire that could be used internationally, the Quick Environment Exposure Sensitivity Inventory (QEESI©), to assist researchers and clinicians in evaluating patients and populations for chemical sensitivity. The Japanese version of QEESI©was subsequently translated by Ishikawa and Miyata (1999). The present study was performed to investigate the reliability and validity of QEESI©(Japanese version) for research purposes and for evaluation of patients with MCS in Japan.

A total of 498 subjects were recruited from the general population of Miyagi prefecture, Japan. The factor structure in QEESI©was analyzed with 40 items on four subscales except for the items in ‘Masking’ using principal components analysis with Promax rotation. The results showed that 30 items on three subscales, ‘Chemical Inhalant Intolerances,’ ‘Symptom Severity,’ and ‘Life Impact’ except for ‘Other Intolerances’ were consistent with those reported for the US population by Miller and Prihoda (1999a). Cronbach’s a reliability coefficient ranged between 0.87 and 0.94 indicating high internal consistency in the 30 items on three subscales.

Next, we compared the mean scores on three subscales of QEESI©in two groups: 131 self-reported MCS group who were new outpatients at the Environmental Medical Center in Kitasato Institute Hospital, and 131 members of the general population (controls) who were matched for both gender and age with the self-reported MCS group. Mean scores on each subscale for the self-reported MCS group were significantly greater than those for controls (PB < 0.001). Mean scores on all of the 30 items on three subscales for the self-reported MCS group were also significantly greater than for the controls (PB < 0.001). These findings indicated that the 30 items on three subscales in QEESI©can be used for surveys and for diagnostic assessment of patients with MCS as well as for comparative studies between patients in Japan and in other countries.

Colorimetric monitoring of formaldehyde in indoor environment using built-in camera on mobile phone

A simple monitoring system of indoor air pollution is proposed by integrating a novel colorimetric detector of formaldehyde (HCHO) and a function of a built-in camera on mobile phone. The colorimetric detector employs a solid phase colorimetric reagent made from 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, ZnO, KIO4 and agar, and changes colour from white to purple by exposure to HCHO gas. The degree of colour changes expressed in Red, Green and Blue model model responded to the HCHO concentration levels both in air and from building materials. Limit of quantitation of the detector with 24 h-exposure resulted in 0.011 mg/m(3) of air concentration which meets a requirement of methodology to detect indoor air quality guideline level of HCHO set by World Health Organization. The detector is also applicable to classify HCHO-emitting materials at least into Type 1, whose emission flux is greater than 120 μg/m(2)/h, and others. Then, variation of the acquired photo images was investigated by using various mobile phones and changing conditions of photography. As a result, the calibration of the measured colour intensity with a colour standard reduced the variation of the results and gave a significant output when the auto-focused images were taken under the condition of common indoor environment.

Allergological and toxicological aspects in a multiple chemical sensitivity cohort

Background. Multiple chemical sensitivity (MCS) is a chronic condition characterized by an exaggerated response to toxicants. We ascertained the prevalence of allergy to metals and toxicological aspects in MCS patients. Methods. We conducted a retrospective review of medical records of 41 patients with MCS. We performed patch testing (n = 21) for dental series and did lymphocyte transformation test (n = 18) for metals. We measured mercury in samples of blood (n = 19), urine (n = 19), saliva (n = 20), and scalp hair (n = 17) to investigate the association between mercury levels and cases of MCS. Results. The prevalence of metal immune hypersensitivity in a subset of 26 patients was 92.3 percent. Elevations of mercury occurred in 81.2 percent (26 of 32). The mean (±SD) in blood concentrations of mercury was 7.6 ± 13.6 μg/L; mean in urine was 1.9 ± 2.5 μg/L; mean in scalp hair was 2.2 ± 2.5 μg/g; mean in saliva was 38.1 ± 52.1 μg/L. Subgroup analyses showed that elevation of mercury levels in biological matrices were associated with mercury amalgams in patients with MCS (22 patients), compared with controls (8 patients) (odds ratio 11 : 95 percent confidence interval 1.5 to 81.6; P = 0.023). Conclusions. Our data show an increased prevalence of metal allergy and elevation of mercury levels in bioindicators among patients with MCS.

Review of evidence for a toxicological mechanism of idiopathic environmental intolerance

Idiopathic environmental intolerance (IEI) is a medically unexplained disorder characterised by a wide variety of unspecific symptoms in different organ systems and attributed to nontoxic concentrations of chemicals and other environmental factors that are tolerated by the majority of individuals. Both exposure to chemicals and behavioural conditioning are considered as possible contributors to the development of IEI. However, owing to the heterogeneity of the condition, it is difficult to separate the toxicological, physiological and psychological aspects of IEI. Here, we review the evidence for postulated toxicologically mediated mechanisms for IEI. Available data do not support either a classical receptor-mediated or an idiosyncratic toxicological mechanism. Furthermore, if there were convincing evidence for a psychological cause for many patients with IEI, then this would suggest that the priority for the future is the development of psychological treatments for IEI. Finally, we advocate genome wide screening of IEI patients to elucidate genotypic features of the condition.

Chemical intolerance in primary care settings: prevalence, comorbidity, and outcomes

PURPOSE

This study extends previous community-based studies on the prevalence and clinical characteristics of chemical intolerance in a sample of primary care clinic patients. We evaluated comorbid medical and psychiatric disorders, functional status, and rates of health care use.

METHODS

A total of 400 patients were recruited from 2 family medicine clinic waiting rooms in San Antonio, Texas. Patients completed the validated Quick Environmental Exposure and Sensitivity Inventory (QEESI) to assess chemical intolerance; the Primary Care Evaluation of Mental Disorders (PRIME-MD) screen for possible psychiatric disorders; the Dartmouth-Northern New England Primary Care Cooperative Information Project (Dartmouth COOP) charts for functional status; and the Healthcare Utilization Questionnaire.

RESULTS

Overall, 20.3% of the sample met criteria for chemical intolerance. The chemically intolerant group reported significantly higher rates of comorbid allergies and more often met screening criteria for possible major depressive disorder, panic disorder, generalized anxiety disorder, and alcohol abuse disorder, as well as somatization disorder. The total number of possible mental disorders was correlated with chemical intolerance scores (P <.001). Controlling for demographics, patients with chemical intolerance were significantly more likely to have poorer functional status, with trends toward increased medical service use when compared with non-chemically intolerant patients. After controlling for comorbid psychiatric conditions, the groups differed significantly only regarding limitations of social activities.

CONCLUSIONS

Chemical intolerance occurs in 1 of 5 primary care patients yet is rarely diagnosed by busy practitioners. Psychiatric comorbidities contribute to functional limitations and increased health care use. Chemical intolerance offers an etiologic explanation. Symptoms may resolve or improve with the avoidance of salient chemical, dietary (including caffeine and alcohol), and drug triggers. Given greater medication intolerances in chemical intolerance, primary care clinicians could use the QEESI to identify patients for appropriate triage to comprehensive nonpharmacologic care.

The association between idiopathic environmental intolerance and psychological distress, and the influence of social support and recent major life events

OBJECTIVES

Idiopathic environmental intolerance (IEI) is a disorder characterized by non-specific symptoms attributed to common airborne chemicals. Increasing evidence points to an association between IEI and symptoms of psychological distress. However, whether other risk factors influence this association has not been clarified. The objective of this study was to examine the association between psychological distress and IEI and to determine whether the association is confounded by social support and major life events.

METHODS

Data were collected by postal questionnaires; other results from the study have been published previously in this journal. The study included participants from a general population-based study who had reported symptoms of chemical sensitivities (n = 787) and two patient groups. The first patient group (n = 101) included individuals who had contacted the Danish Research Centre for Chemical Sensitivities, and the second included individuals who had been diagnosed with environmental intolerance (n = 136). Multiple, hierarchical linear regression analyses were conducted with four IEI-related domains, i.e., mucosal and CNS symptoms, chemical intolerances and social consequences, as the dependent variables, and psychological distress, social support and major life events as the independent variables.

RESULTS

Our study confirmed positive and statistically significant associations between psychological distress and IEI. The associations remained statistically significant after adjusting for major life events and social support.

CONCLUSIONS

The results suggest that the association between IEI and psychological distress cannot be explained by known risk factors. More studies, including longitudinal studies, are needed to determine the role of psychological distress in the development and course of IEI.

Functional somatic syndromes, anxiety disorders and the upper airway: a matter of paradigms

The relationship between the functional somatic syndromes, anxiety disorders and the upper airway (particularly, sleep disordered breathing) remains ambiguous. This ambiguity, despite a growing body of research supporting a relationship, may result from the absence of a paradigm to explain how upper airway dysfunction can promote disorders commonly associated with one's mental health. This review models the functional somatic syndromes and anxiety disorders as consequences of chronically increased hypothalamic-pituitary-adrenal axis activity. It then examines the literature supporting a relationship between these disorders and upper airway dysfunction during wakefulness and sleep. Finally, building upon an existing paradigm of neural sensitization, sleep disordered breathing is linked to functional somatic syndromes and anxiety disorders through chronic activation of the hypothalamic-pituitary-adrenal axis.

Neurotoxicity of toluene

Chemical susceptibility is triggered by a large range of chemicals present both indoors and outdoors including pesticides, cleaning products, perfumes, scented products and cigarette smoke. Health risk after chemical exposure depends on age, sex, genetic factors, socioeconomic status, nutritional status, and environmental factors. Toluene is one of volatile organic chemicals that causes different sensitivity in individuals. Although neurotoxic and immunotoxic effects of toluene have been studied extensively, the underlying mechanism remains obscure. This review highlights the possible neuroimmune factors influencing toluene sensitivity and neurotoxicity in a mouse model.

Attention bias and sensitization in chemical sensitivity

OBJECTIVE

We investigated whether persons with self-reported chemical sensitivity (CS) have an attention bias and enhanced sensitization to chemical exposure.

METHODS

Chemosomatosensory, olfactory, and auditory event-related potentials (ERPs) were recorded from 21 CS subjects and 17 controls in attend and ignore conditions. Reaction times (RTs) and magnitude estimations of perceived intensity were collected in the attend condition. ERPs were averaged over attention conditions and during the first/second part of the testing.

RESULTS

ERP patterns indicated that CS subjects did not habituate to the same extent as the controls and had difficulties ignoring the chemical exposure. CS subjects had faster overall RT, and the perceived intensities for the chemosomatosensory stimuli did not decrease with time in the CS group, which was the case for the controls.

CONCLUSIONS

These results indicating attention bias and enhanced sensitization in CS suggest alterations in central, cognitive responses to chemical exposure.

On the relation between capsaicin sensitivity and responsiveness to CO2: detection sensitivity and event-related brain potentials

OBJECTIVE

Sensory hyperreactivity (SHR) with predominantly airway symptoms is a subgroup of chemical intolerance to various environmental substances with pungent/odorous properties. The hallmark of SHR is sensitivity to capsaicin inhalation, resulting in extensive coughing likely to be mediated by a C-fiber hyperreactivity of the airway sensory neurons. However, it is not clear whether capsaicin sensitivity implies a greater sensitivity to chemosomatosensory substances in general. Therefore, the present study tested the hypothesis of an association between capsaicin cough sensitivity and sensitivity to CO(2) with respect to detection sensitivity and electrophysiological brain response.

METHODS

A correlational study was employed to investigate the relation between capsaicin cough sensitivity and detection thresholds and chemosomatosensory event-related potentials (ERPs) for CO(2) presented in the nasal cavity in 35 persons varying in capsaicin cough sensitivity.

RESULTS

Number of coughs were found to correlate negatively with CO(2) threshold and tended to correlate negatively also with N1 and P2 latencies of the chemosomatosensory ERP for CO(2). No tendencies of correlations were found between number of coughs and latencies for olfactory and auditory ERPs, recorded for comparison, but, unexpectedly, were found between number of coughs and auditory N1 amplitude.

CONCLUSIONS

The results imply that capsaicin cough sensitivity, such as in SHR, is related to higher detection sensitivity, and tends to be related to faster cortical processing of other chemosomatosensory substances, at least of CO(2).

Effect of chronic topical exposure to low-dose noxious chemicals and stress on skin sensitivity in mice

It has been suggested that the recent increase in inflammatory diseases is related to an increase in environmental chemicals and psychiatric stress. To investigate the effect of chronic topical exposure to chemicals and isolation stress, low-dose formalin (a mild contact sensitizer and an irritant), 2,4,6-trinitrochlorobenzene (TNCB; a potent contact sensitizer) and sodium lauryl sulphate (SLS; an irritant) were applied to mouse ears at 7-d intervals under no-stress or stress conditions. Skin reactions (ear swelling) elicited by formalin and TNCB increased time dependently. At the chronic stage, a significant skin reaction peaking at 1 h after application was elicited on the formalin-treated sites, while a shift from a delayed-type hypersensitivity to an immediate-type response was observed on the TNCB-treated sites. At the formalin-treated sites, genes related to neurogenic inflammation, i.e., bradykinin (BK) B2 receptor, IL-6, and membrane metallo endopeptidase (NEP) mRNA were upregulated. In the TNCB-treated sites, marked upregulation of IFN-gamma, IL-1beta, IL-4, and IL-6 mRNA was observed in addition to B2 receptor mRNA. Pretreatment with HOE140, the B2 receptor antagonist suppressed these skin reactions. Increased skin sensitivity to an unrelated chemical, ethanol, and thermal stimuli were elicited in formalin and TNCB-treated mice. Cortisol levels in formalin-treated mice and IgE levels in TNCB-treated mice were elevated respectively. Stress markedly amplified the skin reactions and gene expression related to neurogenic inflammation. SLS did not induce any changes. It was concluded that chronic topical exposure to low-dose noxious chemicals and stress could easily induce skin sensitivity relating to the BK-B2 pathway and nociceptive sensitization reflecting neural sensitization.

Methylmercuric chloride induces activation of neuronal stress circuitry and alters exploratory behavior in the mouse

Methylmercury (MeHg) is a well-known neurotoxicant, responsible for neurological and cognitive alterations. However, there is very little information available on the effects of MeHg administration on activation of murine neuronal pathways involved in the stress response, and whether this is altered as a function of repeated exposure to MeHg. Moreover, interactions between MeHg and other psychogenic and inflammatory stressors have yet to be fully determined. Acute i.p. exposure of male C57BL/6J mice to MeHg (2-8 mg/kg) dose-dependently attenuated exploratory behavior in the open field in the presence and absence of a novel object. In addition, increased numbers of c-Fos immunoreactive cells appeared in response to acute i.p. and i.c.v. MeHg within thalamic (anterior paraventricular nucleus of the thalamus (PVA)/posterior paraventricular nucleus of the thalamus (PV)), hypothalamic (paraventricular nucleus of the hypothalamus (PVN)), central amygdaloid nucleus (CeC), septal and hippocampal (dentate gyrus) nuclei, medial bed nucleus (BSTm) and the locus coeruleus (Lc). The increase in c-Fos positive cells in response to acute i.p. and i.c.v. MeHg did not appear to be influenced further by open field exposure. Repeated administration of MeHg led to an attenuation of most parameters of open field behavior altered by acute MeHg. However, increased c-Fos was significant in the CeC, Dg, supracapsular bed nucleus (BSTs), and Lc. Moreover, open field exposure after repeated treatments resulted in significant c-Fos responses in similar areas. Interestingly, 3 days after the final repeated MeHg dose (2 or 4 mg/kg) c-Fos increases to an immunogenic stressor (LPS) were not affected by MeHg pretreatment. These results demonstrate that systemic exposure to acute and repeated MeHg serves to activate the brain's stress circuitry, and furthermore appears to engage normal neuronal habituation processes.

MMPI-2 Profiles of Persons with Multiple Chemical Sensitivity

We compared the MMPI-2 profiles of adults with multiple chemical sensitivity (MCS), epileptic seizures (ES), and nonepileptic seizures (NES). Both NES and MCS are medically unexplained conditions. In previous studies profiles associated with NES were elevated on scales Hs and Hy, compared with profiles associated with ES. We predicted that profiles associated with MCS would be elevated on Hs and Hy compared with the ES group. Patients with ES and NES were diagnosed after intensive EEG monitoring using published criteria. MCS was diagnosed if there was a complaint of illness in response to multiple common odors at levels that are not noxious to most people. All the MCS cases had legal claims for injury related to chemical exposures. The results showed that on MMPI-2 scales Hs, D, and Hy the MCS group had means significantly higher than both the ES and NES groups. Fake Bad Scale scores were elevated in 11 MCS cases, and regression-based estimates of Fake Bad Scale scores showed elevation in the MCS group compared with both seizure groups. We conclude that MMPI-2 data, obtained from people seeking financial compensation, indicate that there is a strong psychological component to MCS symptoms.

Physiologic and symptomatic responses to low-level substances in individuals with and without chemical sensitivities: a randomized controlled blinded pilot booth study

We conducted a pilot study using a randomized, single-blind, placebo-controlled exposure among 10 individuals with and 7 without reported chemical sensitivities in a dedicated testing chamber. Objectives of the study were to explore the length of the adaptation period to obtain stable readings, evaluate responses to different substances, and measure the level and type of symptomatic and physiologic reactions to low-level exposures. Reported and observed symptoms, electrodermal response, heart rate, skin temperature, surface electromyogram, respiratory rate, contrast sensitivity, and the Brown-Peterson cognitive test were used and compared between cases and controls and between test substances (glue, body wash solution, dryer sheet) and control substances (unscented shampoo and clean air). Subjects with chemical sensitivities (cases) took longer to adapt to baseline protocols than did controls. After adaptation, despite small study numbers, cases displayed statistically significant responses (all measures, p < 0.02) in tonic electrodermal response to test substances compared with controls and compared with the control substance. Symptoms were also higher in cases than in controls for the body wash solution (p = 0.05) and dryer sheets (p = 0.02). Test-retest showed good agreement for both symptoms and tonic electrodermal responses (McNemar's test, p = 0.32 and p = 0.33, respectively). Outside of skin conductance, other measures had no consistent patterns between test and control substances and between cases and controls. This study shows the importance of using an adaptation period in testing individuals with reported chemical sensitivities and, despite small numbers, raises questions about underlying mechanisms and level of reactivity to low-level chemical exposures in sensitive individuals.

The role of corticotropin-releasing factor-like peptides in cannabis, nicotine, and alcohol dependence

The corticotropin-releasing factor (CRF)-like peptides, which include the mammalian peptides CRF, urocortin 1, urocortin 2, and urocortin 3, play an important role in orchestrating behavioral and physiological responses that may increase an organism's chance of survival when confronted with internal or external stressors. There is, however, evidence that a chronic overactivity of brain CRF systems under basal conditions may play a role in the etiology and maintenance of psychiatric disorders such as depression and anxiety disorders. In addition, there is evidence of a role for CRF-like peptides in acute and protracted drug abstinence syndromes and relapse to drug-taking behavior. This review focuses on the role of CRF-like peptides in the negative affective state associated with acute and protracted withdrawal from three widely abused drugs, cannabis, nicotine, and alcohol. In addition, we discuss the high comorbidity between stress-associated psychiatric disorders and drug dependence. A better understanding of the brain stress systems that may underlie psychiatric disorders, acute and protracted drug withdrawal, and relapse to drug-taking behavior may help in the development of new and improved pharmacotherapies for these widespread psychiatric disorders.

Chemosensory perception and event-related potentials in self-reported chemical hypersensitivity

Anormal chemosensory perception has been identified as a possible mechanism underlying odor intolerance, but research in this domain has yet been rather limited. The main objective of the present study was to investigate total perceived intensity, unpleasantness, sensory irritation, and cortical activity assessed with chemosensory event-related potentials (ERPs) for three concentrations of pyridine ranging from predominantly olfactory to trigeminal in activation. Results from 19 individuals with self-reported chemical hypersensitivity and 19 controls with self-reported normal chemical sensitivity show that the hypersensitive group, compared to controls, rated the pyridine stimuli to be more intense and unpleasant, and that these group differences increased with pyridine concentration. Sensory irritation was also the perceptual dimension found to correlate strongest with score on the chemical sensitivity scale. However, no group differences were found in ERP amplitudes or latencies. These findings suggest that self-reported chemical hypersensitivity (1) can be associated with anormal chemosensory perception, (2) may be more closely related to trigeminal function than to olfaction, and (3) has a neural basis at a higher cortical level than that captured by chemosensory ERPs.

Idiopathic environmental intolerance: Part 1: A causation analysis applying Bradford Hill's criteria to the toxicogenic theory

Idiopathic environmental intolerance (IEI) is a descriptor for a phenomenon that has many names including environmental illness, multiple chemical sensitivity and chemical intolerance. Toxicogenic and psychogenic theories have been proposed to explain IEI. This paper presents a causality analysis of the toxicogenic theory using Bradford Hill's nine criteria (strength, consistency, specificity, temporality, biological gradient, biological plausibility, coherence, experimental intervention and analogy) and an additional criteria (reversibility) and reviews critically the scientific literature on the topic. The results of this analysis indicate that the toxicogenic theory fails all of these criteria. There is no convincing evidence to support the fundamental postulate that IEI has a toxic aetiology; the hypothesised biological processes and mechanisms are implausible.

Associations between chemical odor intolerance and sleep disturbances in community-living adults

OBJECTIVE

To investigate associations between sleep disturbances and chemical odor intolerance (COI), which is the subjective report of feeling ill from common odors, such as carpet glue or pesticides.

METHODS

This cross-sectional study consisted of government employees and their family members (n=140; 61% women, mean age=46.3 years) derived from a stratified cluster population living in Pima County, Tucson, AZ. Subjects completed a standard survey that included sleep symptoms, a validated measure of COI, and two questions regarding anxiety and depression. Odds ratios (OR) with 95% confidence intervals (CI) were computed to test the association between COI and sleep symptoms. Stratification according to the Mantel-Haenszel method and logistic regression models were used to test for confounding and/or effect modification.

RESULTS

After adjusting for age and gender, subjects with COI were significantly more likely to report difficulty staying asleep (OR=3.06; CI=1.17-8.03), insufficient sleep (OR=3.93; CI=1.43-10.79), and nightmares (OR=3.17; CI=1.14-8.81) compared to persons without COI. Associations between COI, sleep maintenance problems and insufficient sleep were still significant after adjusting for gender and depression; however, the association between COI and nightmares became borderline.

CONCLUSIONS

Compared to the non-COI, persons with COI are more likely to report sleep maintenance insomnia and insufficient sleep independent of self-reported depression. Nightmares appear to be related more to depression than to COI.

NMDA sensitization and stimulation by peroxynitrite, nitric oxide, and organic solvents as the mechanism of chemical sensitivity in multiple chemical sensitivity

Multiple chemical sensitivity (MCS) is a condition where previous exposure to hydrophobic organic solvents or pesticides appears to render people hypersensitive to a wide range of chemicals, including organic solvents. The hypersensitivity is often exquisite, with MCS individuals showing sensitivity that appears to be at least two orders of magnitude greater than that of normal individuals. This paper presents a plausible set of interacting mechanisms to explain such heightened sensitivity. It is based on two earlier theories of MCS: the elevated nitric oxide/peroxynitrite theory and the neural sensitization theory. It is also based on evidence implicating excessive NMDA activity in MCS. Four sensitization mechanisms are proposed to act synergistically, each based on known physiological mechanisms: Nitric oxide-mediated stimulation of neurotransmitter (glutamate) release; peroxynitrite-mediated ATP depletion and consequent hypersensitivity of NMDA receptors; peroxynitrite-mediated increased permeability of the blood-brain barrier, producing increased accessibility of organic chemicals to the central nervous system; and nitric oxide inhibition of cytochrome P450 metabolism. Evidence for each of these mechanisms, which may also be involved in Parkinson's disease, is reviewed. These interacting mechanisms provide explanations for diverse aspects of MCS and a framework for hypothesis-driven MCS research.

Nasal function in self-reported chemically intolerant individuals

Nasal function has not yet been investigated under controlled exposures in individuals with self-reported Multiple Chemical Sensitivity (sMCS). Therefore, anterior rhinomanometry and acoustic rhinometry were applied in 12 individuals with sMCS, and 12 age-matched controls. The sMCS individuals and controls were selected on the basis of a standardized questionnaire. Controlled 4-hr exposures to ethylbenzene and 2-butanone were performed during 4 sessions. Exposures were close to the current German threshold limit values, and they approximated odor thresholds. Subjects with sMCS had a significant decrease in the flow value in anterior rhinomanometry, independent of substance and doses, compared with controls. This result suggests somatic reactions to the exposure. The result must be confirmed in additional studies, and pathophysiological examinations must be performed. For these investigations, anterior rhinomanometry was usable, but acoustic rhinometry can be recommended only after sufficient standardization has occurred. Furthermore, biochemical parameters of nasal mucosa must be considered.

Homeopathic constitutional type questionnaire correlates of conventional psychological and physical health scales: individual difference characteristics of young adults

This study examined associations between scores for 19 different remedies on the constitutional type questionnaire (CTQ) and scores on standardized psychological and medical trait and state scales from health psychology research. Subjects were 104 young adult American college students (mean age 20 years; 67% female). Scales included the chemical intolerance index (CII) for environmental sensitivity, the NEO personality inventory, Marlowe-Crowne social desirability (MCSD) Scale for defensiveness, Harvard parental caring scale (HPCS) for perceived mother and father traits, Profile of Mood State (POMS) scale, Pennebaker symptom checklist (PSC), and a 3-item global health rating scale. The majority of CTQ constitutional type scores correlated significantly with greater NEO neuroticism, lower MCSD defensiveness, and greater psychological distress on the POMS subscales. NEO Extraversion and Openness subscales correlated with specific CTQ scores in directions consistent with clinical remedy pictures. CTQ Carcinosin differed from other remedies, showing no significant correlations with other scales. As hypothesized (a) persons high on CTQ scores for Carcinosin and low in parental caring (HPCS) had the highest symptom score; (b) those high on CTQ scores for Sulphur and low on HPCS had the poorest global health ratings; (c) individuals high on four different CTQ type scores (Carcinosin, Lachesis, Nux vomica, Sulphur) and high on environmental sensitivity (CII) exhibited the highest symptom scores. Taken together, the data offer additional validation of the CTQ and provide a foundation for studying interactions of constitutional type with both psychosocial and physicochemical environmental factors in homeopathic provers and patients.

Mechanisms of multiple chemical sensitivity

Sensitivity to chemicals is a toxicological concept, contained in the dose-response relationship. Sensitivity also includes the concept of hypersensitivity, although controversy surrounds the nature of effects from very low exposures. The term multiple chemical sensitivity has been used to describe individuals with a debilitating, multi-organ sensitivity following chemical exposures. Many aspects of this condition extend the nature of sensitivity to low levels of exposure to chemicals, and is a designation with medical, immunological, neuropsychological and toxicological perspectives. The basis of MCS is still to be identified, although a large number of hypersensitivity, immunological, psychological, neurological and toxicological mechanisms have been suggested, including: allergy; autosuggestion; cacosomia; conditioned response; immunological; impairment of biochemical pathways involved in energy production; impairment of neurochemical pathways; illness belief system; limbic kindling; olfactory threshold sensitivity; panic disorder; psychosomatic condition; malingering; neurogenic inflammation; overload of biotransformation pathways (also linked with free radical production); psychological or psychiatric illness; airway reactivity; sensitisation of the neurological system; time dependent sensitisation, toxicant induced loss of tolerance. Most of these theories tend to break down into concepts involving: (1) disruption in immunological/allergy processes; (2) alteration in nervous system function; (3) changes in biochemical or biotransformation capacity; (4) changes in psychological/neurobehavioural function. Research into the possible mechanisms of MCS is far from complete. However, a number of promising avenues of investigation indicate that the possibility of alteration of the sensitivity of nervous system cells (neurogenic inflammation, limbic kindling, cacosomia, neurogenic switching) are a possible mechanism for MCS.

EEG beta 1 oscillation and sucrose sensitization in fibromyalgia with chemical intolerance

Patients with fibromyalgia (FM) have diffuse musculoskeletal pain; half report concomitant intolerance for low levels of environmental chemicals (CI). Previous investigators have hypothesized that the chronic pain and chemical intolerance reflect sensitization of different central nervous system limbic and/or mesolimbic reward pathways. We evaluated electroencephalographic (EEG) beta activity and blood glucose responses of FM patients with and without CI and normals during three repeated sucrose ingestion sessions and during a final, water-only session (testing for conditioning). The FM with CI exhibited oscillation (reversal in direction of change from session to session) at rest and then sensitization (progressive amplification) of EEG beta 1 over time across the 3 sucrose sessions versus controls. FM with CI showed sensitization of blood glucose over the 3 sucrose sessions, which, like the EEG findings, reverted toward baseline in the final water-only session. The data suggest that the subset of FM patients with CI have increased susceptibility to oscillation and physiological sensitization without conditioning, perhaps contributing to fluctuations in their chronic course.

Spinal cord neuroplasticity following repeated opioid exposure and its relation to pathological pain

Convincing evidence has accumulated that indicates neuroplastic changes within the spinal cord in response to repeated exposure to opioids. Such neuroplastic changes occur at both cellular and intracellular levels. It has been generally acknowledged that the activation of N-methyl-D-aspartate (NMDA) receptors plays a pivotal role in the development of neuroplastic changes following repeated opioid exposure. Intracellular cascades can also be activated subsequent to NMDA receptor activation. In particular, protein kinase C has been shown to be a key intracellular element that contributes to the behavioral manifestation of neuroplastic changes. Moreover, interactions between NMDA and opioid receptors can lead to potentially irreversible degenerative neuronal changes in the spinal cord in association with the development of opioid tolerance. Interestingly, similar cellular and intracellular changes occur in the spinal cord following peripheral nerve injury. These findings indicate that interactions exist in the spinal cord neural structures between two seemingly unrelated conditions-chronic opioid exposure and a pathological pain state. These observations may help understand mechanisms of chemical intolerance and multiple chemical sensitivity as well as have significant clinical implications in pain management with opioid analgesics.

Acquiring symptoms in response to odors: a learning perspective on multiple chemical sensitivity

In this chapter, a learning account is discussed as a potential explanation for the symptoms in multiple chemical sensitivity. Clinical evidence is scarce and anecdotal. A laboratory model provides more convincing results. After a few breathing trials containing CO2-enriched air as an unconditioned stimulus in a compound with harmless odor substances as conditioned stimuli, subjective symptoms are elicited and respiratory behavior is altered by the odors only. Also, mental images can become conditioned stimuli to trigger subjective symptoms. The learning effects cannot be explained by a response bias or by conditioned arousal, and they appear to involve basic associative processes that do not overlap with aware cognition of the relationship between the odors and the CO2 inhalation. Learned symptoms generalize to new odors and they can be eliminated in a Pavlovian extinction procedure. In accordance with clinical findings, neurotic subjects and psychiatric cases are more vulnerable to learning subjective symptoms in response to odors. Consistent with a learning account, cognitive-behavioral treatment techniques appear to produce beneficial results in clinical cases. Several criticisms and unresolved questions regarding the potential role of learning mechanisms are discussed.

Representation of acute and persistent pain in the human CNS: potential implications for chemical intolerance

The study of pain may be relevant to the study of chemical intolerance (CI) in many ways. Pain is often reported as a symptom of CI and it is defined as a subjective experience similar to many other symptoms of CI, making its objectification difficult. Furthermore, the CNS plastic changes that underlie the development of persistent pain states and abnormal pain responses may share some similarities with those involved in the sensitization to environmental chemicals. Functional brain imaging studies in humans demonstrate that acute pain evoked by nociceptive stimulation is accompanied by the activation of a widely distributed network of cerebral structures, including the thalamus and the somatosensory, insular, and anterior cingulate cortices. Abnormal activity within these regions has been associated with the experience of pain following damage to the peripheral or central nervous system (neuropathic pain) in a number of clinical populations. In normal individuals, activity within this network is correlated with subjective pain perception, is highly modifiable by cognitive interventions such as hypnosis and attention, and has been associated with emotions. Other cognitive mediators such as expectations can also produce robust changes in pain perception (e.g., in placebo analgesia). These effects likely depend on both higher-order cerebral structures and descending mechanisms modulating spinal nociceptive activity. These psychological processes can be solicited to reduce clinical pain and we speculate that they may further attenuate or promote central mechanisms involved in the transition from acute to persistent pain states. The investigation of central determinants of subjective experience is essential to assess the possibility that higher-order brain/psychological processes modulate and/or mediate the development of persistent pain states. These factors may contribute to the development of symptoms in CI.

Sensitization studies in chemically intolerant individuals: implications for individual difference research

Chemical intolerance (CI) is an individual difference trait in which persons report feeling ill in multiple physiological systems from low levels of a wide range of chemically unrelated environmental substances. This paper discusses the neural sensitization model for progressive host amplification of polysymptomatic responses elicited by chemical exposures following an initiating event. The sensitization model accommodates hypotheses for initiating and eliciting CI in human populations that involve both environmental chemicals and physical or psychological stressors. Recent studies in this laboratory have demonstrated sensitization in individuals with CI over repeated sessions for dependent variables such as electroencephalographic (EEG) activity and diastolic blood pressure. Psychological distress variables alone do not explain these findings. Individuals with CI and/or vulnerability to sensitization share specific characteristics, for example, female gender, certain genetic background (offspring of alcohol-preferring parents), and personal preference for high sugar/ carbohydrate intake. Overall, the data suggest that the 15-30% of the general population who report heightened CI are highly sensitizable. Sensitizability may serve an adaptive, sentinel function in threatening environments with poor signal-to-noise ratios. However, as sensitization gradually shifts operating set points of physiological systems out of the normal range in response to allostatic load, this process may contribute to the development of chronic, polysymptomatic health conditions such as multiple chemical sensitivity and/or fibromyalgia. Individual response specificity and stereotypy rather than toxicant properties may determine which types of central, autonomic, and/or peripheral nervous system dysfunctions manifest at subclinical and clinical levels.

Does the kindling model of epilepsy contribute to our understanding of multiple chemical sensitivity?

Multiple chemical sensitivity (MCS) is a phenomenon whereby individuals report an increased sensitivity to low levels of chemicals in the environment. Kindling is a model of synaptic plasticity whereby repeated low-level electrical stimulation to a number of brain sites leads to permanent increases in seizure susceptibility. Stimulation that is initially subthreshold for subclinical seizure provocation comes, over time, to elicit full-blown motor seizures. Kindling can also be induced by chemical stimulation, and repeated exposures to some pesticides have been shown to induce signs of behavioral seizure, facilitate subsequent electrical kindling, and induce subclinical electrographic signs of hyperexcitability in the amygdala. Many of the symptoms of MCS suggest that CNS limbic pathways involved in anxiety are altered in individuals reporting MCS. Limbic structures are among the most susceptible to kindling-induced seizures, and persistent cognitive and emotional sequelae have been associated with temporal lobe epilepsy (TLE) in humans and kindling in animals. Thus, a number of parallels exist between kindling and MCS phenomena, leading to initial speculations that MCS may occur via a kindling-like mechanism. However, kindling requires the activation of electrographic seizure discharge and has thus been primarily examined as a model for TLE. Events leading to the initial evocation of a subclinical electrographic seizure have been much less well studied. It is perhaps these events that may serve as a more appropriate model for the enhanced chemical responsiveness characteristic of MCS. Alternatively, kindling may be useful as a tool to selectively increase sensitivity in subcomponents of the neural fear circuit to address questions relating the role of anxiety in the development and expression of MCS.