Immunological and respiratory changes in animal food processing workers

A group of 35 men employed in the processing of animal food was studied to assess the relation between respiratory findings and immunological status. The most frequent positive skin prick reactions to occupational allergens were to fish flour (82.9%), followed by carotene (77.1%), corn (65.7%), four‐leaf clover (62.9%), sunflower (54.3%), chicken meat (31.4%), soy (28.6%), and yeast (22.7%). Increased total IgE serum levels were found in 14/35 (40.0%) animal food workers compared to 1/39 (2.6%) in a healthy population (p < 0.01). A significantly higher prevalence of chronic respiratory symptoms was found among the exposed workers compared to control workers. There was however, no significant difference in the prevalence of chronic respiratory symptoms between animal food workers with positive and negative skin tests to house dust or to fish flour or among those with increased or normal IgE (except for dyspnea). The frequency of acute symptoms associated with the work shift was high among the animal food workers but similar by immunological status. There were significant mean across‐shift reductions for all ventilatory capacity tests, being particularly pronounced for FEF₂₅. Workers with positive skin tests to fish flour antigen had significantly larger across‐shift reductions in FEF₂₅ than workers with negative skin reactions. An aqueous extract of animal food dust caused a dose‐related contractile response of isolated guinea pig tracheal muscle in vitro. Our data suggest that, in addition to any immunological response animal food dust may produce in vivo, it probably also causes direct irritant or pharmacological reactions on the airways as suggested by our in vitro data.