Introduction Laboratory animal workers (LAW) working with mice are exposed to mouse allergens (MA). Exposure to MA can lead to occupational allergies and asthma. If MA are spread to home environments, the longer duration of exposure might increase the risk for allergic symptoms. Little is known about the spreading of MA. This study aimed to assess:

• whether spreading of MA from workplace to home environment takes place,

• which factors increase spreading of MA.

Methods In a cross-sectional study we took dust samples from the homes of 107 LAW and 13 controls. From 90 LAW we took additional dust samples from their working place. Samples were analysed using mus m 1 ELISA kits. Through a questionnaire we assessed socio-demographic data, allergies and cleaning habits. In LAW we also assessed types of cages used, work tasks and protective clothing.

Results MA concentration was higher in home environments of LAW (median (ng mus m1)=11.3) than in controls (median=1.1; p=0.016; Kruskal-Wallis test). The highest workplace MA concentration was found in the scullery (median=145,0000.0), followed by the changing rooms (median=10.2) and staffrooms (median=7.5). MA concentration was higher in homes of LAW who fulfilled cleaning tasks (cleaning of cages, floors, etc.) (p=0.034) and who changed their linen at home less than once a month (p=0.024). MA concentration at home was not associated with duration of mouse contact (p=0.909) and age of sleeping mattress at home (p=0.649).

Discussion Spreading of MA from workplace to home environment takes place. LAWs who fulfilled cleaning tasks were found to have higher MA concentration at home. Special focus should be given to reduce MA concentration during cleaning in laboratory animal facilities.