Background: The development of simple and standardised methods to measure airborne levels of workplace biological allergens is an important step in reducing the incidence of occupational asthma. Such a method would be useful for measuring wheat flour allergens which cause asthma in bakers. Measurement of allergen per se rather than total dust enables exposure to be better defined. Methods: Monoclonal antibodies were produced, their specificity analysed by immunoblotting and then used to affinity-purify a putative flour allergen. The importance of this protein as an allergen was tested by RAST using sera from allergic bakers and it was identified by N-terminal sequencing. Suitable monoclonal antibodies were chosen to develop an enzyme-linked immunosorbent assay. Commercial baking flours and personal airborne dust samples were analysed using the immunoassay. Results: A sensitive and specific monoclonal antibody-based enzyme-linked immunosorbent assay was developed to measure a wheat α-amylase inhibitor. The wheat α-amylase inhibitor content of bulk wheat flours was 0.124 (95 confidence limits 0.083–0.164) and airborne levels in bakeries had a geometric mean of 744 ng/m3 (95 confidence limits 371–1,496 ng/m3). Conclusion: This assay is suitable for widespread use as the monoclonal antibodies and standards are well defined and potentially infinitely available. The assay therefore offers distinct advantages over those exposure assessment methods currently in use. Comparable results would be obtained by different investigators over a prolonged time period. The assessment of flour allergen exposure and the relationship with clinical response could then be investigated using a multi-centered app
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