The Role of Furry Pets in Eczema

MRCP, Centre of Evidence-based Dermatology, Queen's Medical Centre, Nottingham NG7 2UH, England.
Archives of dermatology (Impact Factor: 4.79). 01/2008; 143(12):1570-7. DOI: 10.1001/archderm.143.12.1570
Source: PubMed


To systematically search, summarize, and critically appraise the literature to examine whether pet exposure in early life is associated with an increased risk of eczema.
We searched MEDLINE (1950 to June 2006) supplemented by citation lists in retrieved articles and contact with researchers. No language restrictions were imposed.
Cohort studies were sufficiently similar to allow pooled analysis. Meta-analysis was not possible for cross-sectional studies owing to differences in methods and populations.
Incidence or prevalence of eczema.
Evidence from longitudinal studies showed that previous exposure to cats (pooled odds ratio [OR], 0.76; 95% confidence interval [CI], 0.62-0.92), dogs (pooled OR, 0.68; 95% CI, 0.53-0.87), or "any furry pet" (pooled OR, 0.79; 95% CI, 0.74-0.84) is associated with a lower risk of eczema. However, in the only cohort study adjusted for avoidance behavior, this "protective effect" disappeared (for cats: OR, 0.80; 95% CI, 0.33-1.97). Stratified analysis by family history in 2 birth cohort studies showed that dog exposure was protective in patients with atopic families. For cats, 1 study showed reduced risk in atopic families only; the other study showed no effect. Eight cross-sectional studies evaluated past pet exposure; a protective effect was seen in 3 studies for cat, dog, or any pet; no study demonstrated an increased risk.
There was no clear evidence that early pet exposure is associated with increased risks of subsequent eczema. We found some evidence of a possible protective effect of early pet exposure, but this might be explained by avoidance behavior in high-risk families.

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    • "This means that, in practice, it is very difficult to determine children’s exact level of exposure to the various fuels or residues released at home by indoor systems. On the other hand, due to lacking data, this study has not attempted to assess the degree of exposure to fuels in closed places other than their home where children spend much of their time (i.e., schools), the presence of other allergens in domestic environments (i.e., mould, dust, mites, etc.) [32,33], dietary habits [34] or alternative variables which represent in a more accurate way the social status of the family. Accordingly, it should be taken into account the possible presence of residual confounding in the present analysis. "
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    • "et al., 2007). Out of 11 cohort and crosssectional studies, five reported significant decreases in eczema risk, yet no significant increases were observed, suggesting that dog exposure may be protective against childhood eczema (Langan et al., 2007). Further, we found that children who were exposed to dog and carried the CT or TT genotype at CD14–159C/T had the lowest risk for eczema at both ages 2 and 3. "
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