National prevalence of asthma and chemical hypersensitivity: an examination of potential overlap.

Objective: The objective of this study was to investigate the linkage between asthma and chemical hypersensitivity.

Methods: The authors conducted a population study with a random sample of 1057 geographically weighted cases to determine the prevalence of both asthma and chemical hypersensitivity in the American population and to explore their co-occurrence.

Results: A total of 14.1% of the respondents reported being diagnosed with asthma and 11.2% reported a hypersensitivity to chemicals. Of those with asthma, 27.2% also reported being hypersensitive to chemicals and 7.4% reported also being diagnosed with multiple chemical sensitivities (MCS). Of those diagnosed with MCS, 42% reported also being diagnosed with asthma. Additionally, 29.7% of those with asthma said air fresheners caused breathing difficulties, and 37.2% found scented products irritating.

Conclusions: The results indicate that there is significant overlap between some forms of asthma and chemical hypersensitivity.