BACKGROUND: Supermarket bakers are exposed not only to flour and alpha amylase but also other 'improver' enzymes, the nature of which is usually shrouded by commercial sensitivity. We aimed to determine the prevalence of sensitisation to 'improver' enzymes in UK supermarket bakers. METHODS: We examined the prevalence of sensitisation to enzymes in 300 bakers, employed by one of two large supermarket bakeries, who had declared work related respiratory symptoms during routine health surveillance. Sensitisation was determined using radioallergosorbent assay to eight individual enzymes contained in the specific 'improver' mix used by each supermarket. RESULTS: The prevalence of sensitisation to 'improver' enzymes ranged from 5% to 15%. Sensitisation was far more likely if the baker was sensitised also to either flour and or alpha amylase. The prevalence of sensitisation to an 'improver' enzyme did not appear to be related to the concentration of that enzyme in the mix. CONCLUSIONS: We report substantial rates of sensitisation to enzymes other than alpha amylase in UK supermarket bakers; in only a small proportion of bakers was there evidence of sensitisation to 'improver mix' enzymes without sensitisation to either alpha amylase or flour. The clinical significance of these findings need further investigation but our findings indicate that specific sensitisation in symptomatic bakers may not be identified without consideration of a wide range of workplace antigens. This article is protected by copyright. All rights reserved.