Cross-reaction between aromatic isocyanates (TDI and MDI): a specific bronchial provocation test study.

A study was performed on twenty-five workers exposed to polyurethane varnishes exclusively catalysed with TDI, who developed asthma to this substance. The aim of the study was to establish, using bronchial provocation tests, whether a cross-response to MDI exists. The results were positive but no definitive evidence has been reached because there was cross-response in only 48% of cases. It is interesting, however, that cross-responders did not predominate among the subjects with a late reaction to TDI (P = 0.0038), whereas cross-responders were in the majority among the subjects with a dual reaction to TDI (P = 0.0334). It is possible that the pattern of the asthmatic reaction to BPT with TDI influences the cross-reaction to other isocyanates.