Submitted:
10 July 2026
Posted:
14 July 2026
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Abstract
Multiple Chemical Sensitivity (MCS) is a chronic condition characterized by adverse reactions on exposure to low-level environmental chemical exposures, often resulting in multisystem symptoms triggered by substances such as volatile organic compounds (VOCs) from fragranced personal and household products. The condition emerges as public health and accessibility issues, as people with MCS may face barriers to accessing workplaces, healthcare settings, educational institutions, and other public environments. This study aims to describe the chemical exposures associated with the onset of the condition (sensitization) and subsequent symptom provocation in MCS, and to characterize symptom patterns and links with known transient receptor potential (TRP) receptor sensitization models. A cross-sectional survey was administered to Canadian residents aged 18 years or older, living with MCS for at least 1 year, with 18 questions assessing exposure history and associations with onset of MCS and symptom provocation. A total of 119 participants completed the survey. Condition onset often occurred at home (35%) and/or in the workplace (55%), following ongoing exposures (61%). Scents, such as perfumes and/or essential oils, including scented air fresheners, cleaning products, construction materials, disinfectants, and laundry products, were associated with both onset and subsequent symptom triggering. Symptoms involved multiple organ systems, with nearly one-third of participants reporting 11 or more symptoms. Cognitive and respiratory symptoms were most prevalent. Third-hand exposure may represent an underrecognized exposure pathway.
Keywords:
multiple chemical sensitivity
; transient receptor potential (TRP)
; environmental exposure
; fragranced consumer products
; symptom profiles
; third-hand exposure
; environmental health
; accessibility
1. Introduction
Multiple chemical sensitivity (MCS), also known as Fragrance Sensitivity, Chemical Intolerance, or Toxicant-Induced Loss of Tolerance [1,2], is a chronic condition characterized by provocation of multisystem symptoms upon exposure to everyday low-level chemical pollutants, including VOCs emitted from fragranced personal care and household products [3]. The health effects include a wide range of symptoms, such as migraines, dizziness, nausea, and breathing difficulties [4], which recur reproducibly following exposure and typically improve or resolve when the trigger is removed from the environment [5,6]. The duration is usually minutes to hours but can last much longer [7]. In this study, the term “trigger” refers to a chemical substance that elicits symptoms upon exposure, at levels previously tolerated prior to the onset of MCS and tolerated by others. Common MCS triggers include VOC-emitting products such as scented laundry products and cleaning supplies, as well as pesticides, smoke, exhaust, renovation materials, and paint.
The ubiquitous presence of VOC sources in built environments (workplaces, healthcare facilities, residences) raises significant public health concerns, as exposure becomes nearly unavoidable. Hence, individuals with MCS frequently report challenges remaining in or re-entering public spaces due to exposure-related symptom exacerbation [8].
With the condition increasing in prevalence in both the United States and Canada [9,10,11], and recent Statistics Canada Canadian Community Health Survey (CCHS) data indicating that Multiple Chemical Sensitivity (MCS) is a significant and growing public health issue, understanding and characterizing its triggers, as well as its mechanisms, is essential for informing prevention, exposure reduction, accommodation strategies, and public policy. Preliminary 2025 Statistics Canada data suggest that approximately 3.1 million Canadian adults (9.4%) reported MCS, while approximately 900,100 adults (2.7%) reported a medical diagnosis [12]. These findings indicate that the population affected by MCS may be substantially larger than diagnosis-based estimates alone suggest and underscore the importance of understanding environmental exposures associated with symptom onset and provocation, as well as the broader implications for healthcare, accessibility, and public health planning.
Recent advances identifying potential mechanisms and biomarkers [13] provide key evidence that MCS onset may be initiated through upregulation and sensitization of chemosensitive transient receptor potential (TRP) receptors following exposures to agonists (such as certain chemicals/VOCs or inflammatory mediators), as well as by oxidative stress. The onset of the condition is often reported to be associated with high-dose chemical exposure of short duration [14]. Symptom expression repeatedly occurs when exposed to a broader range of structurally unrelated chemicals at lower levels, previously tolerated by affected individuals and typically tolerated by the general population [5,6,15].
While current epidemiological studies have focused on prevalence or symptom burden [11], relatively few have examined environmental conditions at onset or the specific chemical exposures associated with subsequent symptom provocation. This study aims to contribute to and extend the growing body of literature by quantifying both direct and indirect chemical exposures and contextualizing findings within TRP receptor sensitization models. From an occupational health and accessibility perspective, these findings will also serve as a baseline for understanding barriers to healthcare access [16] and accommodation needs in home and workplace settings.
2. Materials and Methods
An online cross-sectional survey was conducted. The survey was created by the research team, consisting of specialist physicians, expert scientists, and people with lived experience of MCS. To ensure content validity, the survey was reviewed and pilot-tested before the study began, with input from people experiencing MCS and a panel of clinicians. Participants accessed the survey via an open link on the Qualtrics XM platform (Qualtrics, LLC), a secure web-based data collection survey tool. Those unable to access the online survey were offered to complete it by telephone, conducted by trained staff.
This study was reviewed and approved by the Women’s College Hospital Research Ethics Board (Protocol # 2020-0157-E). Participants were treated in accordance with the principles outlined in the Declaration of Helsinki. All participants provided informed consent electronically. To maintain confidentiality, participant data were de-identified (identified only by an ID number in all databases).
Recruitment and data collection occurred during the COVID-19 pandemic, specifically between January 19 and February 12, 2021. Participants were recruited via 2 websites (Association pour la santé environnementale du Québec—Environmental Health Association of Québec [ASEQ-EHAQ] and the Environmental Health Clinic, at Women’s College Hospital, Toronto, Canada), on social media platforms (Facebook, Twitter, Instagram) and via email through the ASEQ-EHAQ mailing list.
The target population consisted of Canadian residents aged 18 years or over, proficient in either English or French, who had experienced MCS symptoms for at least one year prior to March 11, 2020. If eligible, and upon consent, participants were directed to the main questionnaire, which included 81 questions, of which 18 (relevant to this paper) were analyzed. The extracted questions delve into (i) exposures linked to the onset of the condition, (ii) the symptom profiles linked to subsequent exposures, (iii) indirect exposures through scents transferred on others and items, and (iv) the unsafe housing prevalence. As the study was conducted during the COVID-19 pandemic, selected questions also assessed the effectiveness of masks designed to protect against infection, as protective measures to reduce exposure-related symptoms.
For the purpose of this study, the word “scent” refers to perfumes, fragrances, colognes, and/or essential oils. Third-hand exposure is defined here as exposure to chemical residues left by a previous use of a triggering chemical (e.g., fragrances, smoke, exhaust).
Data analysis was conducted using SPSS v.28. All data were cleaned prior to analysis. Quantitative data from survey responses were summarized using descriptive statistics (frequencies and percentages) to describe participant characteristics, onset environments, initiating exposures, triggering exposures, unsafe housing conditions, and symptom profiles. Some survey items contained missing responses and were treated as N/A. Percentages were hence calculated based on the number of valid responses for each item.
3. Results
3.1. Participant Characteristics
Of the 119 respondents, 103 (87%) were female. The largest age group was 55-64 years (n=43, 36%). Most participants held a university degree (n=68, 57%) or a college degree (n=40, 34%) (Table 1).
3.2. Onset of MCS
Most respondents (n = 108, 91%) reported that MCS began in everyday environments. Workplaces were the most frequently reported location of onset (n = 66, 55%), followed by the home (n = 42, 35%) (Table 2).
More than half (n=72, 61%) indicated ongoing multiple exposures over a period of time as the main factor associated with onset of the condition (Table 3). Other participants attributed the onset to a series of significant exposures (n=36, 30%) or a single large exposure event (n=20, 17%).
Among participants who reported workplace onset (N=66) , scented air fresheners were the most frequently reported exposures associated with onset (n=30, 45%) (Table 4). This is followed by exposure to scents (n=29, 44%), and to industrial cleaning products (n=24, 36%). Other workplace exposures reported to have initiated the condition include construction or renovation materials (n=22,33%), mould spores/water-damaged buildings (n=20, 30%), disinfectants or soaps (n=20, 30%), paint (n=17, 26%), furniture or carpeting (n=16, 24%), pesticides or insecticides (n=15, 23%), photocopier emissions (n=15, 23%), and diesel or vehicle exhaust (21%).
3.3. Exposures to Disinfectants/Soaps and Reported Symptoms Despite Wearing Masks
Among the 119 participants, 112 participants (94%) reported experiencing symptoms upon breathing emissions from scented disinfectants, and 64 (54%) upon inhaling unscented disinfectants, despite wearing masks. Similarly, for soaps, 107 participants (90%) reported experiencing symptoms upon inhaling scented soaps, and 23 participants (19%) upon inhaling unscented soaps, despite mask use (Table 6).
On exposure to scented disinfectants, the most commonly reported symptoms were headaches (n=84, 71%), brain fog or concentration difficulties (n=78, 66%), fatigue (n=73, 61%), breathing difficulties (n=75, 63%), irritability (n=72, 61%), and coughing (n=65, 55%). Symptom distribution was similar for scented soaps, with headaches (n=78, 66%), brain fog (n=75, 63%), fatigue (n=65, 55%), breathing difficulties (n=72, 61%), and irritability (n=70, 59%) (Table 7).
3.4. Infiltration of Triggers into the Home Environment
Participants furthermore reported exposure to triggers entering their living environment from external sources. Emissions from laundry products were the most frequently selected triggers (n=85, 71%). This is followed by scents (n=76, 64%), disinfectants/sanitizers (n=70, 59%) and cleaning products (n=67, 56%) (Table 8).
Among the top chemical exposures entering the home environment (laundry products, scents, disinfectants, and cleaning products), scents were identified by 41 participants (37%) as triggering the largest number of symptoms (11-19). This is followed by cleaning products (n=42, 35%), disinfectants/sanitizers (n=37, 31%), and laundry products (n=34, 29%). Most participants (29-37%) reported between 11-19 symptoms, while a smaller proportion (24-33%) reported 6–10 symptoms or 1–5 symptom ranges (18-30%).
Table 9.
Number of symptoms experienced per exposure.
| Most common exposures entering the lived environment | Number of participants reporting 11–19 symptoms n (%) |
Number of participants reporting 6–10 symptoms n (%) |
Number of participants reporting 1–5 symptoms n (%) |
Number of participants who did not answer n (%) |
|---|---|---|---|---|
| Scents (perfume, cologne) | 41 (37%) | 30 (27%) | 33 (30%) | 7 (6%) |
| Cleaning products | 42 (35%) | 39 (33%) | 21 (18%) | 17 (14%) |
| Disinfectants/sanitizers | 37 (31%) | 32 (27%) | 31 (26%) | 19 (16%) |
| Laundry products | 34 (29%) | 29 (24%) | 31 (26%) | 25 (21%) |
Upon exposure to the above triggers, the most commonly reported symptoms included brain fog (59–69%), headaches (56–68%), fatigue (59–68%), breathing difficulties (60–64%), and irritability (50–61%). Other frequently reported symptoms were memory difficulties (45–56%), dizziness (45–54%), and coughing (46–56%) (Table 10).
3.5. Housing
Eighteen participants (15%) reported unstable housing (including being homeless, moving frequently or living in a vehicle, tent, or with friends and family (Table 11). More than half of participants (n=62, 52%) reported living in unsafe housing, defined as residential units contaminated with mould, emissions from materials such as new paint, renovations, fragranced cleaning products, and/or infiltration of triggers from neighbouring units.
3.6. Indirect/Third-Hand Exposures
Third-hand exposure to disinfectants refers to contact with chemical residues that persist on items that were exposed to a pollutant source (e.g., tobacco smoke) or were handled by a person using fragranced products or disinfectants/sanitizers. Among the 110 participants who answered questions on indirect exposures, 74% (n=81) reported experiencing symptoms from scents on people/items during assisted shopping (situations in which participants relied on another person to shop for their essential needs). Among the 81 participants reporting symptoms, 53% (n=43) reported severity as severe and 42% (n=34) reported as moderate.
When asked about the actions taken for items with transferred scents, more than half of participants reported having to remove the packaging of the item (n=61, 68%), place the items outside to off-gas the scent (n=55, 61%), or dispose of them altogether (n=41, 46%) (Table 12).
4. Discussion
This study provides an overview of the context and exposure patterns associated with the onset and subsequent triggering of symptoms in MCS.
Survey results revealed several key patterns worth highlighting: (i) MCS onset often occurs in everyday environments associated with ubiquitous chronic or repeated low-level exposures, or from single higher exposure events; (ii) fragranced and cleaning product exposures were frequently identified at both onset of the condition and as subsequent triggers of symptoms; (iii) symptoms involve multiple organ systems, with cognitive and respiratory symptoms most frequently reported, which is consistent with the literature [4,38]; (iv) unsafe housing conditions (exposure to symptom triggers from neighbours, renovation materials, or paint) is a potential compounding factor leading to homelessness; and (v) third-hand exposure may be an underrecognized yet prevalent trigger.
4.1. Initiation Patterns, Onset, and Initial Receptor Sensitization
In this study, the vast majority of participants (91%) attributed the onset of MCS to workplace or home environments, highlighting that MCS is more likely to be initiated in non-industrial, non-catastrophic contexts, consistent with the literature [17]. Furthermore, the observation that 61% of participants reported sensitization from ongoing exposure over time highlights repeated low-level exposure to everyday chemicals in the home or workplace (e.g., the routine use of fragranced cleaners, air fresheners, etc.) as a risk factor for developing MCS [18]. Survey responses also highlighted that fragranced consumer products (such as perfumes, air fresheners, cleaning products, and laundry detergents) in the home were frequently associated with the onset of the condition, followed by exposures to construction/renovation activities and pesticides. This is mirrored in workplace exposures, where respondents identified the presence of air fresheners and industrial cleaning products as the main exposures associated with the onset of MCS.
This trend is observed in several other reviews. In Caress and Steinemann [19], respondents reported that their original hypersensitivity was produced by exposure to pesticides (27.5%), solvents (27.5%), new construction/building materials (17.4%), and gasoline or other petroleum products (15.9%). Miller [1] identified two broad classes of MCS initiators: synthetic organic chemical derivatives (VOCs and pesticides) and biogenic toxicants (e.g., mould). In Masri et al. [14], the category of mixed VOCs and semi-volatile organic compounds (SVOCs) was the most prevalent exposure implicated in potential MCS initiation across exposure events, followed by pesticides and combustion products. In Hojo et al. [20], exposure to indoor air contaminants such as renovations (63.2%) and pesticides (27.4%) was also identified as an onset factor for the condition.
Cumulatively, our findings are consistent with the transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) receptor sensitization models [6], whereby initial significant or chronic exposures to everyday pollutant sources are believed to sensitize the individual through TRP sensitization, thereby lowering their chemical tolerance threshold over time. Furthermore, in line with our findings, the models highlight synthetic organic chemicals (e.g., VOCs from fragranced and cleaning products, renovation materials, pesticides) and biogenic toxicants (e.g., mould) as the two broad classes of initiators.
In Claeson and Andersson [21], for example, masked exposure to acrolein, a TRPA1 agonist, elicited symptom responses in individuals with MCS, suggesting TRPA1-mediated sensory sensitization. TRPA1 is the most broadly tuned chemosensory channel known [22], and acrolein is a ubiquitous VOC formed during incomplete combustion of gasoline and oil, tobacco smoke, and reactions between ozone and components of indoor air [23,24,25]. Past animal studies also highlighted behavioural and neurochemical sensitization from repeated exposures to solvents and aldehydes (including toluene and formaldehyde, often emitted from cleaning products, renovation materials, etc.) [26,27,28].
4.2. The Spreading Phenomenon
Receptor sensitization is then followed by a “spreading phenomenon”, whereby the chemical intolerance widens to include a larger range of diverse chemicals and a lower tolerance threshold. This phenomenon refers to the well-documented clinical observation that sensitivity initially confined to one chemical irritant or mixture expands over time to encompass multiple, chemically unrelated exposures. This occurs because, once sensitized, TRPV1 and TRPA1 are more easily sensitized to other agonists [29,30,31], as explained by established sensitization mechanisms [32,33,34,35,36]. In other words, sensitized individuals will react to significantly lower concentrations of a larger set of unrelated chemicals [1].
This is illustrated in participant responses. The same categories of exposures that contributed to the onset of the condition remain primary symptom triggers: scents, cleaning, laundry, and disinfectants. Furthermore, participants also reported reacting to triggers from external sources (e.g., laundry emissions infiltrating their home environment or neighbourhood).
According to Gibson and Vogel [37], once MCS has developed, primary symptom triggers include pesticides, formaldehyde, fresh paint, perfume, and air fresheners. Findings were further supported by Steinemann [9], who found that 67.6% of participants identified air fresheners and deodorizers as triggering health problems, 57.9% identified scented laundry products coming from dryer vents, and 67.6% identified being in a room cleaned with scented products as a trigger.
Additionally, our findings reveal that nearly three-quarters of the participants (74%) identified third-hand exposures as a symptom-triggering factor. This finding, which does not appear to be quantified in the literature, potentially highlights an emerging challenge for individuals with MCS and an under-recognized exposure pathway.
The increased use of disinfectants and sanitizers during the COVID-19 pandemic appears to have introduced a new layer of risk, with 44% of participants reporting disinfectants as symptom-triggering, 96% of whom reported symptoms upon inhalation.
4.3. Symptom Profiles
Survey results reveal a significant symptom load, involving multiple organ systems, with cognitive and respiratory symptoms dominating.
A notable first trend is indeed the high proportion of participants reporting 11–19 symptoms upon exposure to triggers (e.g., 35% of participants reported 11–19 symptoms upon exposure to cleaning products). This is also the case for scents and fragrances, where 37% of participants reported 11–19 symptoms, and for laundry products, where 29% of participants reported 11–19 symptoms. The wide range of reported symptoms (from respiratory to dermatologic and gastrointestinal) furthermore highlights the involvement of multiple organ systems and is consistent with the most commonly used case criteria for the diagnosis of MCS [39,40,41]. This high and diverse symptom load is similarly observed in Saito et al. [42], where nearly 17 symptoms were identified, and in Fares-Medina et al. [41], where more than half of female participants (59%) reported two or more symptoms (from musculoskeletal to genitourinary). In Hausteiner et al. [43], more than a third of participants reported five or more symptoms.
Reported symptoms fell into two main categories: cognitive and respiratory. Cognitive impairments included brain fog, memory difficulties, and irritability (affecting 45–69% of participants across various triggers). Respiratory symptoms included breathing difficulties and coughing (46–64%). The prevalence of cognitive and respiratory symptoms has also been well documented in recent studies. In a study by Fares-Medina et al. [42], airway and mucous membrane alterations were often the first symptoms that manifested (68.9% of participants). Del Casale et al. [4] reported similar trends with a high prevalence of respiratory and neurocognitive symptoms. In a case study by Guerrero et al. [44], symptoms were similarly categorized into two main groups: respiratory (52% of cases) and neurological (29%). These trends were similarly observed in a study by Steinemann [9], in which the most commonly reported symptoms were respiratory difficulties (50.3% of respondents) and migraine or headaches (46.9%).
4.4. Limitations and Future Research
This study contains some limitations worth noting. First, the findings rely on self-reported data, which often requires recalling the context and nature of exposures that led to the onset of their condition. Self-reporting can be subject to recall bias and inaccuracies. Secondly, voluntary participation may have additionally introduced self-selection bias into the sample. Furthermore, although the inclusion criteria ensured that participants had lived with MCS for at least a year, the study did not require clinical confirmation of diagnosis. However, due to documented difficulties in obtaining a formal diagnosis [16], reliance on self-identification appeared as the most feasible option. Finally, the findings are specific to the Canadian context; therefore, although similarities were found in other studies, our findings may not be directly generalizable to populations in other countries with different exposure types.. Despite these limitations, this paper adds to an under-researched area on MCS, by quantifying exposure patterns (locations, sources) involved in the onset and subsequent triggering of symptoms. Future research expanding the body of knowledge on third-hand exposures is recommended (e.g., quantifying chemical residues or assessing the economic burden of disposing of contaminated items). Furthermore, as data collection occurred during the COVID-19 pandemic, a repeated cross-sectional survey would allow comparison of exposure patterns and symptom profiles during and after the pandemic. Finally, given that the next epidemic cannot be predicted, it is recommended that research be conducted proactively to ensure that disinfectant products are fragrance-free, have the lowest VOC emissions, and are tested for human and environmental health.
5. Conclusions
This study provides a detailed description of environmental exposures at the onset of MCS and during subsequent triggering of symptoms. Delving into the circumstances of sensitization and symptom triggers, the survey findings are consistent with TRPV1 and TRPA1 receptor sensitization models, highlighting repeated low-level exposure to everyday chemicals (particularly those in fragrances and cleaning products) as key drivers of both sensitization and triggering stages. Notably, the results highlight indirect or third-hand exposures as an under-recognized exposure pathway leading to real-life consequences, such as the disposal of recently purchased contaminated household items (including food), thereby adding an additional economic burden.
The findings furthermore underscore the breadth and severity of symptom burden, with more than a third of participants experiencing 11 or more symptoms on exposure to triggers. Although cognitive and respiratory symptoms were most common, the extent of symptom categories highlights the involvement of multiple organ systems, which vary significantly from one individual to another.
This heterogeneity (in trigger source, symptom type, and severity) creates several significant barriers in healthcare, including obtaining a formal diagnosis, further compounded by limited medical training. Whereas a formal medical diagnosis is required for accommodation, limited knowledge among medical providers of the condition results in a lack of support for accommodation and inclusion in all spheres of accessibility (including workplace, housing, and healthcare). Addressing this challenge, therefore, necessitates targeted responses. Though tools and guidelines already exist, integrating them with enhanced and continuous training of healthcare providers, in parallel with appropriate workplace accommodation measures to reduce chemical exposures (such as fragrance-free practices and the selection of least-toxic products in terms of VOC emissions), is essential to ensure adequate and equitable access to public, occupational, and healthcare settings.
Supplementary Materials
The following supporting information can be downloaded at the website of this paper posted on Preprints.org, Table S1: Survey questions.
Author Contributions
Conceptualization, R.P.; methodology, R.P., J.M., and R.B.; validation, R.P., J.M., and R.B.; formal analysis, N.A.D.; investigation, R.P., J.M., and R.B.; data curation, N.A.D.; writing—original draft preparation, N.A.D.; writing—review and editing, R.P., J.M., R.B., and A.T.; visualization, N.A.D.; supervision, R.P.; project administration, R.P.; funding acquisition, R.P. All authors have read and agreed to the published version of the manuscript.
Funding
Funding for this study was provided by the Association pour la santé environnementale du Québec—Environmental Health Association of Quebec (ASEQ-EHAQ).
Institutional Review Board Statement
The study was conducted in accordance with the Declaration of Helsinki, and approved by the Institutional Review Board (or Ethics Committee) of Women’s College Hospital Research Ethics Board (Protocol #2020-0157-E).
Informed Consent Statement
Informed consent was obtained from all subjects involved in the study.
Data Availability Statement
The data sets generated and analyzed during this study are available from the corresponding author upon reasonable request.
Acknowledgments
The authors thank all the participants experiencing multiple chemical sensitivity (MCS) who took the time and the effort to contribute to the study.
Conflicts of Interest
Some authors received remuneration from (ASEQ-EHAQ) for conducting data analysis and manuscript preparation. However, this did not influence the study design, analysis, or interpretation of results.
Appendix A. Survey Questions
| Item | Responses possible |
| General Information – Screening Questions | |
| Q1. What is your age? | Less than 18 [end of survey if selected] 13 categories of 10-year intervals from age 18 to age 79 80+ |
| Q2. Country of residence | Canada Other [end of survey if selected] |
| Q3. When did you start experiencing symptoms of multiple chemical sensitivity MCS? | Before March 11, 2019 Between March 11, 2019 and present [end of survey if selected] Not applicable, I do not suffer from MCS [end of survey if selected] |
| Demographics | |
| Q4. What is your sex? | Female Male Other Prefer not to answer |
| Q5. What is the highest level of education that you have completed? | Less than secondary school Secondary school graduation Post-secondary education Undergraduate degree Post-graduate certificate Master’s degree Doctorate or Postdoctoral degree Prefer not to answer |
| MCS Onset and Triggers | |
| Q6. Do you know where your chemical sensitivity/MCS was initiated/started? (Select all that apply) | Home Workplace Other Unsure |
| Q7. Which of the following household exposures do you think initiated your condition? (Select all that apply) | Construction or renovation materials Cooking odors Cleaning products Engine exhaust Disinfectants Foods Furnishings Laundry products Mould Scents Air fresheners Pesticides Woodstove emissions Unknown source Other |
| Q8. Which of the following workplace exposures do you think initiated your condition? (Select all that apply) | Chemicals from laboratory Construction or renovation materials Cooking odors Diesel or vehicle exhaust Disinfectants or soaps Foods Furniture or carpeting Industrial cleaning products Lacquer/varnish Mould spores/water-damaged building Paint Scented air fresheners Pesticides or insecticides Photocopier emissions Printing ink Scents Solvents Textiles or fabrics Tobacco smoke Unknown source Other |
| Q9. Was your MCS health condition initiated by | A single large exposure event Ongoing exposure/s over a period of time A series of significant exposures Unsure Other |
| Q10. Do you experience symptoms when inhaling the following despite wearing a mask? |
Each with: Yes/No/Not applicable Unscented disinfectant/Sanitizer Scented disinfectant/sanitizer Unscented soap Scented soap |
| Q11. Please indicate your symptom(s) upon exposure, if any, to the following when inhaled: |
Dropdown list includes (for each of the above triggers) Brain fog or concentration difficulties Memory difficulties Fatigue Dizziness Coordination or balance difficulties Headaches Irritability Ear problems Eye problems Breathing difficulties Coughing Joint and muscle pain Muscle weakness Itching Other skin problems Cardiovascular problems Gastrointestinal problems Urinary problems Other symptoms |
| Housing Conditions | |
| Q12. Do you live in safe housing suitable for your MCS health condition?(Safe housing is as follows and should be free of the following: mould, materials that trigger your symptoms (such as paint, new construction/renovation materials), exposures to triggers from neighbours or nearby emissions from traffic or industry, etc. | Yes No |
| Q13. What is your current housing situation? (Select all that apply) | Affordable/social housing homeless owner moving frequently renting shelter tent vehicle with family/friends other |
| Exposure to Odours & Symptoms | |
| Q14. Were you/are you exposed to the following odours from external sources? |
Each with: Yes/No/Not applicable Cleaning products Cooking odours Disinfectants/sanitizers Scents Home renovation Incense Laundry products Second/third-hand tobacco smoke Second/third-hand marijuana |
| Q15. Please indicate symptoms experienced upon exposure to these odours: |
Dropdown list includes (for each of the above odours): Brain fog Memory issues Fatigue Dizziness Breathing difficulties Coughing Headaches Skin problems Cardiovascular issues Gastrointestinal problems Other |
| Indirect Exposure Through Others | |
| Q16. If you are dependent on others for shopping and they use scented products, do you experience symptoms from the scents on the person or items? | Yes No Not applicable |
| Q17. Rate the severity of your symptoms on exposure to these scents | Severe Moderate Mild |
| Q18. What do you do with the items that have scents transferred to them during handling? | Clean them vigorously Remove the packaging Put them outside to off-gas the odour of the scent Dispose of them in the garbage Not applicable |
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Table 1.
Sociodemographic characteristics.
| Sample Characteristics | n (N=119) | % | |
|---|---|---|---|
| Sex | |||
| Male | 16 | 13% | |
| Female | 103 | 87% | |
| Age group (years) | |||
| 25-34 | 9 | 8% | |
| 35-44 | 23 | 19% | |
| 45-54 | 19 | 16% | |
| 55-64 | 43 | 36% | |
| 65-74 | 19 | 16% | |
| 75 and over | 6 | 5% | |
| Education | |||
| Secondary school | 9 | 7% | |
| College | 40 | 34% | |
| University | 68 | 57% | |
| Prefer not to answer | 2 | 2% | |
Table 2.
Location of MCS onset.
| Location | n (N=119) | % | |
|---|---|---|---|
| Workplace | 66 | 55 | |
| Home | 42 | 35 | |
| Other | 30 | 25 | |
| Unsure | 4 | 3 |
*Totals may exceed 100% because participants could select multiple responses.
Table 3.
Exposure events associated with onset of MCS.
| Event | n (N= 119) | % |
|---|---|---|
| Ongoing exposure/s over a period of time | 72 | 61 |
| A series of significant exposures | 36 | 30 |
| Other** | 24 | 20 |
| Unsure | 21 | 18 |
| A single large exposure | 20 | 17 |
*Totals may exceed 100% because participants could select multiple responses. ** ‘Other’ responses include: ‘mould, bleach, urea-formaldehyde over a period of months’, ‘two (exposure) events’ and ‘35 years working as a hairdresser’.
Table 4.
Workplace exposures associated with onset of MCS.
| Trigger | n (N= 66) | % |
|---|---|---|
| Scented air fresheners | 30 | 45% |
| Scents | 29 | 44% |
| Industrial cleaning products | 24 | 36% |
| Construction or renovation materials | 22 | 33% |
| Disinfectants or soaps | 20 | 30% |
| Mould spores/water-damaged building | 20 | 30% |
| Paint | 17 | 26% |
| Furniture or carpeting | 16 | 24% |
| Pesticides or insecticides | 15 | 23% |
| Photocopier emissions | 15 | 23% |
| Diesel or vehicle exhaust | 14 | 21% |
| Printing ink | 14 | 21% |
| Solvents | 11 | 17% |
| Chemicals from laboratory | 10 | 15% |
| Lacquer/varnish | 10 | 15% |
| Other** | 9 | 14% |
| Unknown source | 8 | 12% |
| Tobacco smoke | 6 | 9% |
| Foods | 3 | 5% |
| Cooking odours | 2 | 3% |
| Textiles or fabrics | 2 | 3% |
* Totals may exceed 100% because participants could select multiple responses. ** ‘Other’ responses included ‘Tobacco, marijuana, smoked street drugs, incense’, ‘Art supplies’, ‘H1N1 influenza’, and ‘house renovations, i.e., paints, cleaners, solvents’.
Table 6.
Self-reported symptoms despite mask use.
| Trigger | n (N = 119) | % | |
|---|---|---|---|
| Unscented disinfectant/sanitizer | |||
| Yes | 64 | 54% | |
| No | 55 | 46% | |
| Scented disinfectant/sanitizer | |||
| Yes | 112 | 94% | |
| No | 7 | 6% | |
| Unscented soap | |||
| Yes | 23 | 19% | |
| No | 96 | 81% | |
| Scented soap | |||
| Yes | 107 | 90% | |
| No | 12 | 10% | |
Table 7.
Symptoms by trigger type (N=119).
| Symptoms | Scented disinfectant/sanitizer n (%) |
Unscented disinfectant/sanitizer n (%) |
Scented soap n (%) |
Unscented soap n (%) |
|---|---|---|---|---|
| Brain fog or concentration difficulties | 78 (66%) | 37 (31%) | 75 (63%) | 10 (8%) |
| Memory difficulties | 64 (54%) | 29 (24%) | 58 (49%) | 10 (8%) |
| Fatigue | 73 (61%) | 36 (30%) | 65 (55%) | 13 (11%) |
| Dizziness | 66 (56%) | 25 (21%) | 58 (49%) | 7 (6%) |
| Coordination or balance difficulties | 52 (44%) | 22 (18%) | 48 (40%) | 5 (4%) |
| Headaches | 84 (71%) | 44 (37%) | 78 (66%) | 14 (12%) |
| Irritability | 72 (61%) | 29 (24%) | 70 (59%) | 11 (9%) |
| Ear problems | 30 (25%) | 16 (13%) | 28 (24%) | 6 (5%) |
| Eye problems | 44 (37%) | 23 (19%) | 43 (36%) | 7 (6%) |
| Breathing difficulties | 75 (63%) | 42 (35%) | 72 (61%) | 13 (11%) |
| Coughing | 65 (55%) | 38 (32%) | 59 (50%) | 11 (9%) |
| Joint and muscle pain | 43 (36%) | 22 (19%) | 42 (35%) | 12 (10%) |
| Muscle weakness | 40 (34%) | 17 (14%) | 40 (34%) | 9 (8%) |
| Itching | 47 (40%) | 24 (20%) | 48 (40%) | 14 (12%) |
| Other skin problems | 34 (29%) | 20 (17%) | 34 (29%) | 11 (9%) |
| Cardiovascular problems | 28 (24%) | 13 (11%) | 26 (22%) | 5 (4%) |
| Gastrointestinal problems | 39 (34%) | 15 (13%) | 37 (31%) | 8 (7%) |
| Urinary problems | 20 (17%) | 9 (8%) | 20 (17%) | 5 (4%) |
| Other symptoms† | 22 (19%) | 13 (11%) | 23 (19%) | 10 (8%) |
* Totals may exceed 100% because participants could select multiple responses. ** ‘Other’ responses included ‘Burning and pain in lungs’, ‘Voice changes’, ‘Burning and irritation in the sinus’, ‘Lip swelling, face and throat swelling’, ‘Difficulty walking’, ‘Rashes, eczema’, ‘Nausea’.
Table 8.
Triggers entering the home environment.
| Trigger | n (N=119) | % |
|---|---|---|
| Laundry products | 85 | 71% |
| Scents | 76 | 64% |
| Disinfectants/sanitizers | 70 | 59% |
| Cleaning products | 67 | 56% |
| Cooking odours | 65 | 55% |
| Second/third-hand tobacco smoke | 45 | 38% |
| Second/third-hand marijuana | 37 | 31% |
| Home renovation | 31 | 26% |
| Incense | 21 | 18% |
*Totals may exceed 100% because participants could select multiple responses.
Table 10.
Symptoms triggered by specific exposures (N=119).
| Symptom | Cleaning products | Disinfectants/sanitizers | Scents (perfume, cologne) | Laundry products |
|---|---|---|---|---|
| Brain fog | 82 (69%) | 74 (62%) | 79 (66%) | 70 (59%) |
| Headaches | 81 (68%) | 76 (64%) | 81 (68%) | 67 (56%) |
| Fatigue | 81 (68%) | 71 (60%) | 75 (63%) | 70 (59%) |
| Breathing difficulties | 73 (61%) | 71 (60%) | 76 (64%) | 73 (61%) |
| Irritability | 71 (60%) | 67 (56%) | 73 (61%) | 60 (50%) |
| Memory difficulties | 67 (56%) | 63 (53%) | 65 (55%) | 54 (45%) |
| Dizziness | 61 (51%) | 55 (46%) | 64 (54%) | 54 (45%) |
| Coughing | 63 (53%) | 58 (49%) | 67 (56%) | 55 (46%) |
| Coordination or balance problems | 48 (40%) | 49 (41%) | 52 (44%) | 42 (35%) |
| Eye problems | 44 (37%) | 45 (38%) | 48 (40%) | 40 (34%) |
| Joint and muscle pain | 55 (46%) | 48 (40%) | 48 (40%) | 42 (35%) |
| Gastrointestinal problems | 48 (40%) | 38 (32%) | 44 (37%) | 42 (35%) |
| Muscle weakness | 42 (35%) | 35 (29%) | 43 (36%) | 39 (33%) |
| Itching | 48 (40%) | 37 (31%) | 39 (33%) | 37 (31%) |
| Ear problems | 31 (26%) | 29 (24%) | 31 (26%) | 23 (19%) |
| Other skin problems | 35 (29%) | 32 (27%) | 29 (24%) | 31 (26%) |
| Cardiovascular problems | 30 (25%) | 27 (23%) | 32 (27%) | 25 (21%) |
| Urinary problems | 23 (19%) | 15 (13%) | 18 (15%) | 18 (15%) |
| Other symptoms† | 29 (24%) | 24 (20%) | 23 (19%) | 24 (20%) |
* Totals exceed 100% because participants could select multiple symptoms for each source. ** ‘Other’ responses included ‘Muscle spasms, arthritis, sore throat, difficulty swallowing’, ‘Face feels swollen, changes in body odour’, ‘Burning and pain in lungs, pain in trunk of body, in head and in liver’.
Table 11.
Housing characteristics of participants.
| Housing characteristic | n (N=119) | % | |
|---|---|---|---|
| Access to safe housing suitable for MCS | |||
| Yes | 57 | 48 | |
| No | 62 | 52 | |
| Current housing situation | |||
| Affordable/social housing | 6 | 5 | |
| Unstable housing (homeless, moving frequently, shelter, tent, vehicle, with family/friends, etc.) | 18 | 15 | |
| Owner | 51 | 43 | |
| Renting | 42 | 35 | |
| Other | 2 | 2 | |
*Percentages may not total 100 due to rounding.
Table 12.
Indirect exposures (third-hand) and severity of symptoms.
| Variable | n (N=110) | % | |
| Symptoms from scents on people/items during assisted shopping* | n (N=110) | % | |
| Yes | 81 | 74 | |
| Not applicable | 29 | 26 | |
| Severity of symptoms reported on indirect exposure to these scents | % | ||
| Severe | 43 | 53 | |
| Moderate | 34 | 42 | |
| Mild | 4 | 5 | |
| Did not answer | 29 | 36 | |
| Actions taken for items with scent transfer during handling | n (N=90) | % | |
| Put them outside to off-gas the odour of the scent | 55 | 61 | |
| Dispose of them in the garbage | 41 | 46 | |
| Clean them vigorously | 49 | 54 | |
| Remove the packaging | 61 | 68 | |
*Assisted shopping refers to situations in which participants relied on another person to shop for their essential needs. ** Totals may exceed 100% because participants could select multiple responses.
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