. Author manuscript; available in PMC: 2020 Jun 10.

Published in final edited form as: Int Forum Allergy Rhinol. 2018 Feb;8(2):108–352. doi: 10.1002/alr.22073

TABLE VI.G.2.

Evidence for the effect of early childhood pet exposure of the development of allergic rhinitis

Study	Year	LOE	Study design	Study groups	Clinical endpoint	Conclusion
Dharmage et al.⁵⁶²	2012	2a	SR	19 studies (2011–2012): 9 longitudinal, 8 cross-sectional, 2 case-control	Association of AR with exposure to cats	Inconsistent association. If exposure during the first year, less AR or sensitization, or no effect. Possible protective effect until adulthood.
Lodge et al.⁶⁴²	2012	2a	SR	(2001–2008): 9 longitudinal studies; 6498 subjects aged 0–11 years	Association of physician diagnosed hay fever with exposure to pets, or cats and dogs during perinatal period in urban environment	Dogs may reduce sensitization or allergic disease in families with low risk of allergy. No association with cats.
Lodrup-Carlsen et al.⁵⁵²	2012	2a	Pooled analysis of individual data first year of recruitment	(1989–1997): 11 European birth cohorts; 11,489 participants aged 6–10 years	Association of sensitization to aeroallergens with ownership of cats only, dogs only, cats and dogs only, birds only or rodents only during 0–2 years of age	Dog and rodent exposure protective against sensitization to aeroallergens. No association with AR.
Smallwood & Ownby⁶⁴¹	2012	2a	SR	26 articles: exposure to dogs 20 weeks from gestation to 1 year.	Association of allergic symptoms with exposure to dogs	Inconsistent association. Dog exposure at birth may be protective against allergic symptoms.
Chen et al.⁶⁴⁰	2010	2a	SR of birth and non-birth cohort studies and cross-sectional studies	62 articles (2000–2009); subjects 6–69 years old: 17 birth cohorts reported cat exposure or Fel d 1 in dust; 13 reported dog ownership or Can f 1 in dust; 26 cross-sectional studies reported cat or dog exposure	Association of AR with exposure to cats or dogs in cross-sectional studies	Inconsistent association. Dog exposure may be protective. Design of the study influences the association.
Takkouche et al.⁶³⁹	2008	2a	Meta-analysis	32 studies (1985–2006); 5 studies (n = 6818) reported rhinitis	Association of AR with exposure to furred pets	Inconsistent association. Possible protective effect of furred pets on rhinitis.
Christensen et al.⁶⁴³	2016	2b	Population based cross-sectional study follow-up	RHINE cohort (2010–2012): 13,376 subjects born in Northern Europe 1945–1973	Association of AR in adulthood with exposure to pets at birth, during childhood and to livestock farm in childhood	Exposure to pets in childhood decreases the risk of AR in adulthood independently of urban or rural upbringing.
Lodge et al.⁵³⁴	2012	2b	Prospective birth cohort	MACS cohort: 620 infants with family history of allergic disease	Association of hay fever after 7 years of age with exposure to cats and dogs at birth	In high-risk cohort, pet exposure at birth is protective against hay fever at age 7 years in children with nonsensitized fathers

AR = allergic rhinitis; LOE = level of evidence; MACS = Melbourne Atopy Cohort Study; RHINE = Respiratory Health in Northern Europe; SR = systematic review.