The role of cats and dogs in asthma and allergy—a systematic review
Studies have reported contradictory effects of cat and dog exposure on allergy, resulting in inconsistent recommendations on animal avoidance. We conducted a systematic review of observational studies published in English from 2000 to January 2009. It shows in this review that the reported exposure-response relationships are contradictory. A total of 17 and 13 birth cohort studies on cat and dog exposure, respectively, are included in the review. Most of the birth cohort studies found that cat or dog exposure in early life had no effect on the development of asthma or wheezing symptoms and dog exposure during infancy was found to protect children from developing sensitization against aeroallergens. A total of 7 and 6 prospective studies in school-age children or adults on cat and dog exposure, respectively, are included in this review and most of these studies suggested an inverse association between cat exposure and asthma and wheezing symptoms. As for cross-sectional studies, 26 and 21 studies on cat and dog exposure, respectively, are included in this review, which cover a broad range of age groups and geographical areas, and reported inconsistent results. The evidence summarised in this systematic review needs to be interpreted with caution, the inconsistent study results may be due to study design, exposure assessment, and avoidance measure. The exposure-response relationships may also alter in geographical areas where the community prevalence of cats and dogs are significantly different. However, as the evidence of the effects of pet keeping on subsequent development of asthma or allergic diseases presented in this review are not overwhelmingly strong, the decision of whether to keep a cat or a dog in the family should be based on arguments other than the concern of developing asthma and allergy.
Available from: Joachim Heinrich
- "Other studies observed positive or non-significant associations between home exposure to cats or dogs and atopy, respiratory symptoms and asthma [21-24]. In addition, a systematic review suggested no association with dog ownership with large heterogeneity across studies . "
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ABSTRACT: Inflammation is a key factor in the pathogenesis of respiratory diseases. Early life exposure to microbial agents may have an effect on the development of the immune system and on respiratory health later in life.In the present work we aimed to evaluate the associations between early life microbial exposures, and fractional exhaled nitric oxide (FeNO) at school age.
Endotoxin, extracellular polysaccharides (EPS) and beta(1,3)-D-glucan were measured in living room dust collected at 2--3 months of age in homes of participants of three prospective European birth cohorts (LISA, n = 182; PIAMA, n = 244; and INMA, n = 355). Home dampness and pet ownership were periodically reported by the parents through questionnaires. FeNO was measured at age 8 for PIAMA and at age 10/11 for LISA and INMA. Cohort-specific associations between the indoor microbial exposures and FeNO were evaluated using multivariable regression analyses. Estimates were combined using random-effects meta-analyses.
FeNO at school age was lower in children exposed to endotoxin at age 2--3 months (beta -0.05, 95% confidence interval (CI) -0.10;-0.01) and in children with reported dog ownership during the first two years of life (GM ratio 0.82, CI 0.70-0.96). FeNO was not significantly associated with early life exposure to EPS, beta(1,3)-D-glucan, indoor dampness and cat ownership.
Early life exposure to bacterial endotoxin and early life dog ownership are associated with lower FeNO at school age. Further studies are needed to confirm our results and to unravel the underlying mechanisms and possible clinical relevance of this finding.
Environmental Health 12/2013; 12(1):103. DOI:10.1186/1476-069X-12-103 · 3.37 Impact Factor
Available from: Bertil Forsberg
- "While observational studies suggest that high levels of exposure to house dust mite (HDM) allergen increase risk of allergic disease
[1,2], intervention studies that reduce HDM allergen levels have failed to show any reduction in asthma or allergic disease outcomes
[3-5]. Similarly, there is insufficient evidence to either recommend pet keeping, or removal, for prevention of allergic disease
[6,7]. It is currently unclear if allergen exposure during pregnancy and early life may help induce tolerance, or promote allergic sensitisation and disease. "
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A seasonal effect of month of birth and risk of allergic disease has been suggested by numerous studies. Few studies have directly measured pollen exposures at different points during pregnancy and in early life, and assessed their effects on risk of respiratory disease outcomes.
Pollen exposure was calculated for the first and last 12 weeks of pregnancy and the first 12 weeks of infancy for all children conceived by women residing in Stockholm, Sweden, between 1988 and 1995. Hospital admission data for respiratory conditions in the first year of life was also collected.
Out of 110,381 children, 940 had been hospitalised for asthma by 12-months of age. Pollen levels showed both marked seasonal variations and between year differences. Exposure to high levels of pollen in the last 12 weeks of pregnancy was associated with an increased risk of asthma hospitalisation (aOR = 1.35, 95% CI = 1.07-1.71 for highest quartile versus remaining infants). Exposure to high levels of pollen in the first three months of life was associated with a reduced risk (aOR = 0.76, 95% CI = 0.59-0.98) but only in children of heavy smoking mothers.
High levels of pollen exposure during late pregnancy were somewhat unexpectedly associated with an elevated risk of hospitalisation for asthma within the first year of life.
Allergy Asthma and Clinical Immunology 11/2012; 8(1):17. DOI:10.1186/1710-1492-8-17 · 2.03 Impact Factor
Available from: De-Wei Li
- "We found children both sensitized and exposed to dog allergen at levels above 1.2 mg/g were at 53% greater risk of wheeze. Most studies in a systematic review of the literature since 2000 on the role of household pets in allergy and asthma (Chen et al., 2010), use report of cat or dog ownership as the exposure measure. In our analyses, when cat or dog ownership is substituted for ''exposed,'' we found no significant relationships with exposure/sensitization status and any of the health outcomes (data not shown). "
American Thoracic Society 2012 International Conference, May 18-23, 2012 • San Francisco, California; 05/2012
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