Korppi M, Hyvärinen M, Kotaniemi-Syrjänen A, Piippo-Savolainen E, Reijonen T. Pediatr Allergy Immunol. 2008;19(8):696–701
PURPOSE OF THE STUDY. Birth cohort studies have suggested that early exposure to furred pets protects from later asthma and allergy. The aim of this study was to evaluate the association between exposure or sensitization to cat or dog in infancy and later asthma and allergy assessed at the median ages of 4.0, 7.2, and 12.3 years.
STUDY POPULATION. Children 1 to 23 months of age who had wheezing and respiratory distress that required hospital care during an acute respiratory tract infection were enrolled.
METHODS. Exposure to cat and dog in infancy was assessed by interviewing the parents. The child was considered to be sensitized if the allergen-specific immunoglobulin E level to cat or dog was ≥0.35 kU/L or if there was a positive skin-test response.
RESULTS. When the 20 children with persistent childhood asthma (doctor-diagnosed asthma at all 3 control visits) were compared with the other 61 children, early exposure to dog (odds ratio [OR]: 0.14; P = .034) decreased the asthma risk, and early sensitization to cat (OR: 5.92; P = .008) and dog (OR: 9.33; P = .001) increased the asthma risk. There was less cat- and dog-keeping in atopic families, and the effect of sensitization was, but the effect of exposure was not, robust to adjustments in multivariate analyses.
CONCLUSIONS. This study demonstrates that, in long-term follow-up evaluation after early wheezing, early sensitization to cat and dog increases the risk of later asthma but early exposure to cat or dog has no such effect. Dog-keeping was less frequent in atopic families, which may explain why the protective effect of early exposure to dog was lost in multivariate analyses.
REVIEWER COMMENTS. Studies have shown that early high-dose exposure to allergens may be protective for the development of allergy, and children who do not develop early allergic sensitization to environmental allergens are at lower risk for having persistent wheezing symptoms. This study's results are consistent with those of previous studies; although early sensitization to cat and dog increases the risk for later asthma in children at high risk, early high-dose exposure to furred animals does not seem to be a risk factor. It should be noted that atopic families tended to have pets less frequently, which might have introduced confounding effects.
- Copyright © 2009 by the American Academy of Pediatrics