Evidence-based medicine (EBM) approaches have recently been applied to occupational asthma.1 2 The EBM document by Newman Taylor et al1 for occupational asthma evaluates, among other issues, the existence of exposure-response relations for sensitisation and asthma. The cited references indeed provide evidence that exposure-response curves exist for certain high molecular weight allergens. The risk for allergen-specific sensitisation and asthma increases steeply with increasing allergen exposure, especially in atopics.3 More sensitised individuals express respiratory symptoms at higher exposure than at low exposure.4 The time to development of allergy is shorter at higher exposures than at lower exposure.5

The question arises of what the implications of all these findings are with regard to primary prevention of allergic respiratory disease? Exposure-response relations suggest that lowering the exposure will reduce the burden of disease. Some direct evidence exists which illustrates that reduction of exposure leads to reduction of disease burden. Reduction of the exposure, by introducing powder-free gloves, led to a reduction in the number of sensitised and asthmatic workers.6 This conclusion is based on ecological evidence as well as longitudinal intervention studies. The effect of exposure reductions on sensitisation in more complex situations, with multiple determinants of exposure, is not as clearly established. Uncertainty exists as to whether the risk for developing enzyme-related sensitisation and asthma …