Skin and Allergy Hospital, Helsinki University Hospital, Helsinki, Finland. University of Helsinki, Helsinki, Finland. Human Microbiome Research (HUMI), Faculty of Medicine, University of Helsinki, Helsinki, Finland. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. DNA Sequencing and Genomics Laboratory, Institute of Biotechnology, Helsinki, Finland. Department of Public Health and Welfare, Finnish Institute for Health and Welfare (THL), Helsinki, Finland. Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland. Finnish Environment Institute, Helsinki, Finland. Department of Biosciences, University of Helsinki, Helsinki, Finland. University of Eastern Finland, Joensuu, Finland. Department of Pulmonary Diseases and Clinical Allergology, University of Turku, Turku, Finland. Allergy Clinic, Terveystalo, Turku, Finland. Finnish Lung Health Association (FILHA), Helsinki, Finland. North Karelia Centre for Public Health, Joensuu, Finland. Pirkanmaa Joint Authority for Health Services and Social Welfare, Tampere, Finland. Institute of Allergology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany. Institute for Translational Medicine and Pharmacology ITMP, Allergology and Immunology, Berlin, Germany. University Hospital Montpellier, Montpellier, France.