Longitudinal study on cat allergen exposure and the development of allergy in young children.

The influence of cat allergen exposure in early childhood on the development of sensitization and allergic diseases is complex. Little is known about the natural course of the sensitization development within individuals. We investigated the association between cat allergen exposure in infancy and cat ownership and cat contact during childhood and the development of cat sensitization and allergic diseases up to age 6 years using a longitudinal analysis approach. Overall, 2166 children from an ongoing birth cohort study were included in the analysis. House dust samples were collected 3 months after birth. Cat allergen levels were extracted. Blood samples were collected when the children were 2 and 6 years old. Information on the allergic symptoms of children and doctor-diagnosed allergic disease were collected at each follow-up using questionnaires. Cat allergen exposure in infancy was positively associated with sensitization at age 2 years but not at age 6 years. No associations existed between cat allergen exposure in infancy and allergic symptoms and diseases up to age 6 years. Cumulative allergen exposure from cat ownership and regular cat contact increased the risk of cat sensitization up to age 6 years. Cat allergen exposure in infancy increases the risk of sensitization development in early childhood but not in school-age children. Cumulative allergen exposure from cat ownership and regular cat contact during childhood contribute to sensitization development up to school age. Cat allergen avoidance at home alone might be not effective to prevent the development of allergic sensitization in young children.