OPS 08: Biological contaminants and respiratory health, Room 117, Floor 1, August 26, 2019, 4:30 PM - 5:30 PM Background: Pets are important sources of endotoxin. Exposure to endotoxin as well as exposure to dog and cat allergens have each been associated with asthma and wheeze. However, it has been difficult to separate the impact of these exposures and whether they interact with each other to affect respiratory outcomes. Methods: We examined whether exposure and sensitization to dog and cat influence the association of house dust endotoxin with asthma and wheeze in 6051 children and adults in the U.S. National Health and Nutrition Examination Survey. Exposure to pets was assessed using both pet ownership and pet allergens measured in bedroom dust. Endotoxin was quantified using the LAL assay. Allergic sensitization status was determined from serum levels of specific immunoglobulin-E. Administered questionnaires assessed current asthma and wheeze and associated morbidities. Results: The study confirmed the prevalence of dog (48.3%) and cat (37.5%) ownership and endotoxin concentration in dust was significantly greater in homes with pets. Exposure to endotoxin as well as exposure and sensitization to dog and cat allergens were each independently associated with a higher prevalence of current asthma and/or wheeze, especially in adults. The association of endotoxin with the respiratory outcomes was significantly altered by exposure to pet allergens and sensitization status. In participants not sensitized to dog, exposure to high levels of dog allergen enhanced the association of endotoxin with wheeze, while in participants sensitized to cat, exposure to high levels of cat allergen heightened the odds of current asthma associated with endotoxin. The concurrent exposure to high levels of both dog and cat allergens augmented the association of endotoxin with both current asthma and wheeze in the past 12 months. Conclusions: We conclude that measures to reduce the levels of endotoxin as well as dog and cat allergens may help prevent active asthma and wheeze.