• 1
    The International Study of Asthma and Allergies in Childhood (ISAAC) Steering Committee. Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema: ISAAC. Lancet 1998;351: 12251232.
  • 2
    Von Hertzen LC, Haahtela T. Asthma and atopy – the price of affluence? Allergy 2004;59: 124137.
  • 3
    Sears MR, Herbison GP, Holdaway MD, Hewitt CJ, Flannery EM, Silva PA. The relative risks of sensitivity to grass pollen, house dust mite and cat dander in the development of childhood asthma. Clin Exp Allergy 1989;19: 419424.
  • 4
    Arshad SH, Karmaus W, Matthews S, Mealy B, Dean T, Frischer T et al. Association of allergy-related symptoms with sensitisation to common allergens in an adult European population. J Investig Allergol Clin Immunol 2001;11: 94102.
  • 5
    Holt PG. Key factors in the development of asthma: atopy. Am J Respir Crit Care Med 2000;161: S172S175.
  • 6
    Strachan DP. Hay fever, hygiene, and household size. BMJ 1989; 299:12591260.
  • 7
    Von Mutius E, Martinez FD, Fritzsch C, Nicolai T, Reitmeir P, Thiemann HH. Skin test reactivity and number of siblings. BMJ 1994;308: 692695.
  • 8
    Jarvis D, Chinn S, Luczynska C, Burney P. The association of family size with atopy and atopic disease. Clin Exp Allergy 1997;27: 240245.
  • 9
    Bodner C, Godden D, Seaton A. Family size, childhood infections and atopic diseases. Thorax 1998;53: 2832.
  • 10
    Haby MM, Marks GB, Peat JK, Leeder SR. Daycare attendance before the age of two protects against atopy in preschool age children. Pediatr Pulmonol 2000;30: 377384.
  • 11
    Ball TM, Castro-Rodriguez JA, Griffith KA, Holberg CJ, Martinez FD, Wright AL. Siblings, day-care attendance, and the risk of asthma and wheezing during childhood. N Engl J Med 2000;343: 538543.
  • 12
    Infante-Rivard C, Amre D, Gautrin D, Malo JL. Family size, day-care attendance, and breastfeeding in relation to the incidence of childhood asthma. Am J Epidemiol 2001;153: 653658.
  • 13
    Svanes C, Jarvis D, Chinn S, Omenaas E, Gulsvik A, Burney P. Early exposure to children in family and day care as related to adult asthma and hay fever: results from the European Community Respiratory Health Survey. Thorax 2002;57: 945950.
  • 14
    Celedon JC, Wright RJ, Litonjua AA, Sredl D, Ryan L, Weiss ST et al. Day care attendance in early life, maternal history of asthma, and asthma at the age of 6 years. Am J Respir Crit Care Med 2003;167: 12391243.
  • 15
    Marbury MC, Maldonado G, Waller L. Lower respiratory illness, recurrent wheezing, and day care attendance. Am J Respir Crit Care Med 1997;155: 156161.
  • 16
    Celedon JC, Litonjua AA, Weiss ST, Gold DR. Day care attendance in the first year of life and illnesses of the upper and lower respiratory tract in children with a familial history of atopy. Pediatrics 1999;104: 495500.
  • 17
    Koopman LP, Smit HA, Heijnen ML, Wijga A, van Strien RT, Kerkhof M et al. Respiratory infections in infants: interaction of parental allergy, childcare, and siblings – The PIAMA study. Pediatrics 2001;108: 943948.
  • 18
    Ball TM, Holberg CJ, Aldous MB, Martinez FD, Wright AL. Influence of attendance at day care on the common cold from birth through 13 years of age. Arch Pediatr Adolesc Med 2002;156: 121126.
  • 19
    Braun-Fahrlander C, Gassner M, Grize L, Neu U, Sennhauser FH, Varonier HS et al. Prevalence of hay fever and allergic sensitization in farmer's children and their peers living in the same rural community. Clin Exp Allergy 1999;29: 2834.
  • 20
    Riedler J, Eder W, Oberfeld G, Schreuer M. Austrian children living on a farm have less hay fever, asthma and allergic sensitization. Clin Exp Allergy 2000;30: 194200.
  • 21
    Von Ehrenstein OS, Von Mutius E, Illi S, Baumann L, Bohm O, von Kries R. Reduced risk of hay fever and asthma among children of farmers. Clin Exp Allergy 2000;30: 187193.
  • 22
    Kilpelainen M, Terho EO, Helenius H, Koskenvuo M. Farm environment in childhood prevents the development of allergies. Clin Exp Allergy 2000;30: 201208.
  • 23
    Ernst P, Cormier Y. Relative scarcity of asthma and atopy among rural adolescents raised on a farm. Am J Respir Crit Care Med 2000;161: 15631566.
  • 24
    Downs SH, Marks GB, Mitakakis TZ, Leuppi JD, Car NG, Peat JK. Having lived on a farm and protection against allergic diseases in Australia. Clin Exp Allergy 2001;31: 570575.
  • 25
    Leynaert B, Neukirch C, Jarvis D, Chinn S, Burney P, Neukirch F, European Community Respiratory Health Survey. Does living on a farm during childhood protect against asthma, allergic rhinitis, and atopy in adulthood? Am J Respir Crit Care Med 2001;164: 18291834.
  • 26
    Portengen L, Sigsgaard T, Omland O, Hjort C, Heederik D, Doekes G. Low prevalence of atopy in young Danish farmers and farming students born and raised on a farm. Clin Exp Allergy 2002;32: 247253.
  • 27
    Hesselmar B, Aberg N, Aberg B, Eriksson B, Bjorksten B. Does early exposure to cat or dog protect against later allergy development? Clin Exp Allergy 1999;29: 611617.
  • 28
    Roost HP, Kunzli N, Schindler C, Jarvis D, Chinn S, Perruchoud AP et al. Role of current and childhood exposure to cat and atopic sensitization. J Allergy Clin Immunol 1999;104: 941947.
  • 29
    Perzanowski MS, Ronmark E, Platts-Mills TA, Lundback B. Effect of cat and dog ownership on sensitization and development of asthma among preteenage children. Am J Respir Crit Care Med 2002;166: 696702.
  • 30
    Litonjua AA, Milton DK, Celedon JC, Ryan L, Weiss ST, Gold DR. A longitudinal analysis of wheezing in young children: the independent effects of early life exposure to house dust endotoxin, allergens, and pets. J Allergy Clin Immunol 2002;110: 736742.
  • 31
    De Meer G, Toelle BG, Ng K, Tovey E, Marks GB. Presence and timing of cat ownership by age 18 and the effect on atopy and asthma at age 28. J Allergy Clin Immunol 2004;113: 433438.
  • 32
    Heinrich J, Gehring U, Douwes J, Koch A, Fahlbusch B, Bischof W et al. Pets and vermin are associated with high endotoxin levels in house dust. Clin Exp Allergy 2001;31: 18391845.
  • 33
    Gereda JE, Klinnert MD, Price MR, Leung DY, Liu AH. Metropolitan home living conditions associated with indoor endotoxin levels. J Allergy Clin Immunol 2001;107: 790796.
  • 34
    Anyo G, Brunekreef B, de Meer G, Aarts F, Janssen NA, van Vliet P. Early, current and past pet ownership: associations with sensitization, bronchial responsiveness and allergic symptoms in school children. Clin Exp Allergy 2002;32: 361366.
  • 35
    Illi S, von Mutius E, Lau S, Bergmann R, Niggemann B, Sommerfeld C et al. Early childhood infectious diseases and the development of asthma up to school age: a birth cohort study. BMJ 2001;322: 390395.
  • 36
    Williams LK, Peterson EL, Ownby DR, Johnson CC. The relationship between early fever and allergic sensitization at age 6 to 7 years. J Allergy Clin Immunol 2004;113: 291296.
  • 37
    Karmaus W, Arshad H, Mattes J. Does the sibling effect have its origin in utero? Investigating birth order, cord blood immunoglobulin E concentration, and allergic sensitization at age 4 years. Am J Epidemiol 2001;154: 909915.
  • 38
    Harris JM, White C, Moffat S, Mills P, Newman Taylor AJ, Cullinan P. New pregnancies and loss of allergy. Clin Exp Allergy 2004;34: 369372.
  • 39
    Sunyer J, Anto JM, Harris J, Torrent M, Vall O, Cullinan P et al. Asthma Multi-centre Infants Cohort Study. Maternal atopy and parity. Clin Exp Allergy 2001;31: 13521355.
  • 40
    Kramer U, Heinrich J, Wjst M, Wichmann HE. Age of entry to day nursery and allergy in later childhood. Lancet 1999;353: 450454.
  • 41
    Apelberg BJ, Aoki Y, Jaakkola JJ. Systematic review: Exposure to pets and risk of asthma and asthma-like symptoms. J Allergy Clin Immunol 2001;107: 455460.