Laboratory animal allergy is preventable in modern research facilities.

Background: Historical data suggest 15% of laboratory animal workers develop IgE sensitisation and 10% symptoms of laboratory animal allergy (LAA), including occupational asthma. Individually ventilated cages (IVCs) are replacing conventional open cages; we sought to evaluate their impact on the development of LAA.

Methods: We surveyed 750 laboratory animal workers and measured airborne Mus m 1 (mouse allergen) levels in seven UK institutions. We compared the prevalence of sensitisation to mouse proteins (by specific IgE assay or skin prick test) and of work-related allergic symptoms in IVC-only and open cage units.

Results: Full-shift Mus m 1 levels were lower in IVC than open cage units (geometric mean 1.00 (95% CI 0.73-1.36) 8.35 (95% CI 6.97-9.95) ng·m; p<0.001), but varied eight-fold across the IVC units (geometric mean range 0.33-4.12 ng·m). Primary analyses on data from 216 participants with ≤3 years exposure to mice revealed a lower prevalence of sensitisation in those working in IVC units compared with conventional cage units (2.4% (n=2) 9.8% (n=13); p=0.052). Sensitisation in IVC units varied from 0% to 12.5%; the use of fitted respiratory protection was less common in IVC units where prevalence of sensitisation was higher. Work-related allergy symptoms were more frequently reported by mouse-sensitised individuals (46.7% 10.9%; p<0.001) and only by those working in open cage units.

Conclusion: In contemporary practice, LAA is now largely preventable with the use of IVC systems and the judicious use of appropriate respiratory protection.