Exposure-response relationships for wheat allergen exposure and asthma

Background: A few studies have investigated exposure-response relationships for sensitisation to wheat, work-related symptoms and wheat allergen exposure. IgG4 is suggested to protect against the development of allergic sensitisation. The main aim of this current study was to explore the nature of exposure-response relationships for a range of clinically relevant endpoints among bakery workers, and to investigate the role of IgG4 in these relationships.

Methods: A cross-sectional study of 517 supermarket bakery workers in 31 bakeries used a questionnaire, serum specific IgE and IgG4 to wheat, and methacholine challenge tests. Mixed effects exposure models for wheat allergens were developed using job, bakery size, tasks and specific ingredients used. These models were used to predict average personal current exposure to wheat allergens in the past year.

Results:  The exposure-response relationships for average exposure followed a bell-shaped curve, with the prevalence of sensitisation, allergic symptoms and probable occupational asthma, increasing up to 10 - 15 µg/m³wheat allergen concentration after which they plateau off and decrease at higher exposure concentrations. This relationship was modified by atopic status. IgG4 levels were strongly exposure related: a clear increase in prevalence of higher IgG4 with increase in wheat allergen exposure was observed among those sensitised and non-sensitised to wheat, with IgG4 even more strongly associated with exposure than IgE to wheat. 

Conclusions: The bell-shaped exposure response relationship in the current study is consistent with the findings of previous studies. IgG4 showed no protective effect for sensitisation, confirming the findings of previous studies, suggesting that the pattern is probably related to a healthy worker effect.