A number of allergens are present indoors. Cat and dog allergens are present in the majority of buildings, including buildings where these animals have never been present and at levels that, in some cases, exceed proposed threshold levels to cause sensitization. Studies performed in several major U.S. inner cities have linked exposure to cockroach, rat and mouse allergens with asthma, and indicate that these allergens account for 95 percent of the indoor allergens present in some cases. Exposure to rodent allergens is also frequent in the middle class and a common cause of occupational allergies in laboratory and animal-care personnel. *IIAQC Newsletter November 2006 Vol.1