IgE-mediated allergy to phytase -- a new animal feed additive.

Although fungal phytase is frequently used as an additive to animal feed few investigations of its allergenic property have been conducted. Fifty-three subjects occupationally exposed to powdered phytase from Aspergillus niger were studied. Exposure data and symptoms were registered by the company physician. Thirty-eight subjects complained of work-related respiratory symptoms and 14 of them showed phytase-specific IgE antibodies; only one asymptomatic subject revealed such antibodies. IgE antibodies were significantly more frequently found in the high-exposure group (technical centre) when compared with the low-exposure group (laboratories, experimental animal husbandry). Phytase-specific IgG antibodies were present in 19 symptomatic (50%) and five (33%) asymptomatic subjects. Our results demonstrate that powdered fungal phytase is a highly sensitizing substance whose inhalation exposure should be avoided. Hypersensitivity symptoms could be prevented by means of extensive hygienic measures and ongoing medical surveillance.