(p. 258) Pet exposure in early life and the development of allergy and asthma 

During the analysis of data from a prevalence study on allergic diseases in 7–9- year-old children from different parts of Sweden, we found indications of a negative correlation relationship between early pet exposure and allergy. The objective of this study was to assess the relationship between exposure to pets early in life, family size and allergic manifestations later during childhood. In the present follow up study we have taken selection mechanisms behind pet keeping into consideration when investigating the relationship between early pet exposure and allergy development. . . . In 1991, a questionnaire study of allergic diseases was conducted in the Göteborg area (Göteborg and Mölndal) on the south-west coast of Sweden, and in Kiruna, a mining town in the northern inland mountains, north of the Arctic Circle. . . . A subsample was selected in 1992 from the main study population for a more detailed interview and skin prick tests (SPT). . . . The 412 children who underwent the validation interview and SPT in 1992 were contacted once again in the winter 1996 for a follow up study . . . Exposure to animals during the first year of life were further analysed in 1996 by detailed questions about type and duration of animal exposure. . . . Pet exposure during first year of life was associated with a lower prevalence of allergic rhinitis at 7–8 years of age, a lower cumulative incidence of asthma and a lower prevalence of asthma at 12–13 years of age.