Background: Because allergic sensitization seems to occur especially during infancy, we decided to evaluate such an exposure in day nurseries. Methods: Thirty day nurseries in Marseilles, which were selected at random, were visited during 2 weeks in April 1993. Routine cleaning includes daily cleaning of smooth floors, weekly laundering of sheets, and monthly cleaning of soft toys. Mattresses are encased in synthetic covers. Dust samples were collected from four settings: infants' mattresses and pillows, smooth floors, and soft toys. Levels of mite, cockroach, cat, and dog allergens were analyzed with a monoclonal antibody-based ELISA. Results: Mite allergen levels were lower than the proposed threshold level for sensitization (2 mu g/gm of dust) on 94% of mattresses and soft toys and on 100% of floors and pillows. Cat allergen levels in mattresses ranged from less than 0.1 to 4.5 mu g/gm dust. On floors, cat allergen levels ranged from less than 0.1 to 2.4 mu g/gm dust. Only 10% of pillows and soft toys had levels greater than 2 mu g/gm of dust. Fel d I levels were significantly higher (p < 0.03) in mattresses from nurseries with curtains and were correlated with the percentage of children with a cat at home. In almost all day nurseries cockroach allergen (Bla g I and Bla g II) levels were very low. Only three samples from mattresses had clog allergen levels greater than 2 mu g of Can f I allergen per gram of dust. On floors the level was always lower than 2 mu g/gm. Conclusions: These data clearly show that indoor allergen levels are much lower in day nurseries than in most houses. Most samples contain allergen levels below threshold levels for sensitization. Thus children of atopic parents are less likely to become sensitized to indoor allergens in day nurseries than in their own homes. In addition, this study emphasizes the efficacy of avoidance measures such as use of synthetic protective mattress covers, frequent washing of sheets and soft toys, and avoidance of carpets and curtains.
