Chemical Exposures, Sensitization, Provocation and Symptom Profiles in Adults with Multiple Chemical Sensitivity: A Cross-Sectional Survey

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.