Birth cohort acronym, study setting, year of recruitment, number of children recruited, and pet ownership during the first 2 years of life in 11 European birth cohorts (sorted from north to south).

ECA: Environment and Childhood Asthma Study. BAMSE: Children, Allergy, Milieu, Stockholm, Epidemiological Survey. DARC: Danish Allergy Research Council Study. PIAMA-NHS: The Prevention and Incidence of Asthma and Mite Allergy – Natural History Study. MAS: Multi-center Allergy Study. LISA: Lifestyle-related Factors on the Immune System and Development of Allergies in Childhood Study. GINI-B: German Infant Nutritional Intervention Study (observational part). AMICS: Asthma Multicentre Infant Cohort Study.1and no other furry or feathered pet.23754 initially recruited and followed-up until 2 years; for ECA: 1877 invited for longer follow-up.3More children are part of the Leicester 1998 cohort, but for the present meta-analyses on early pet ownership we included only children who were recruited during the 1st year of life.