Prevalence of Multiple Chemical Sensitivity in Canada Between 2000 and 2020.

Multiple chemical sensitivity (MCS) describes an acquired condition characterized by recurrent, non-specific symptoms attributed to previously tolerated chemical exposure. Although Canada collects national data on MCS through population health surveys, the condition remains poorly understood and under-studied. This study analyzes data from the Canadian Community Health Survey (2000-2020) to examine trends in MCS prevalence across demographic characteristics, including province of residence, sex, and age. Descriptive analyses were used to assess temporal changes and differences between regions and population subgroups. Between 2000 and 2020, the proportion of Canadians reporting an MCS diagnosis increased from 1.9% to 3.5%. Prevalence varied geographically, with higher rates consistently observed in the Atlantic provinces compared with the Prairie provinces. MCS prevalence increased with age in both sexes; however, rates were higher among young males than females, with this pattern reversing in mid-life as prevalence became higher among females. These findings provide a national overview of MCS prevalence over two decades and offer relevant information for public health authorities, healthcare professionals, and researchers. The observed prevalence aligns with international estimates, underscoring MCS as an emerging public health concern in Canada.