Evolving concepts of chemical sensitivity.

Chemical sensitivity appears to be an elusive phenomenon. Studies on individual differences in susceptibility may provide glimpses into the range of sensitivity in a population, which can be used for further study. Preliminary evidence in laboratory animals suggests the range of sensitivity to manufactured chemicals may span orders of magnitude. Determining the reasons that underlie individual differences in sensitivity is a more difficult enterprise. Conditioning of adverse physiological effects of airborne chemicals may play a vital role in the etiology of chemical sensitivity, and it provides a rigorous laboratory model by which to investigate some aspects of this elusive phenomenon.