Determinants of whether occupational agents cause early, late, or dual asthmatic responses.

Early asthmatic responses to aeroallergens can be predicted from skin prick tests and the level of airway responsiveness. High-molecular-weight occupational agents ought to behave in the same way, but this has not been established sufficiently to allow challenge tests to be avoided. Responses to low-molecular-weight agents are difficult to predict because of the absence of a good measure of sensitization. Late responses appear more common with these agents, but this may be in part a consequence of the single-dose challenge protocol that is commonly used. The pattern of response also is likely to be influenced by the length of time from the last exposure, and the use of medication.