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Exposure to pets in first year of life shown to decrease allergic sensitivity to cats and dogs
Wegienka G. Clin Exper Allergy. 2011;doi:10.1111/j.1365-2222.2011.03747.x.
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Exposure to indoor dogs and cats early in life was associated with a decreased risk for sensitization, according to a study.
Using interview data from participants in the Detroit Childhood Allergy Study, researchers examined the association between lifetime dog and cat exposure and allergic sensitization by age 18 years. Sensitization to dog or cat was defined as animal-specific immunoglobulin E of at least 0.35 kU/L; pets were considered “indoor” if they spent at least 50% of their time in the house. Separate exposure analyses were conducted for dogs and cats, and they were measured according to first year of life, age groups and cumulative lifetime.
The researchers hypothesized that although the mediating mechanisms for pet exposure and allergy development are as yet unknown, pet ownership is associated with exposure “to distinct, more broadly diverse bacterial populations in household dust and that these exposures influence bacterial colonization of the infant gastrointestinal tract, maturation of immune responsiveness, and development of allergen-specific sensitization, total IgE, allergy and atopic asthma.”
Males with an indoor dog during the first year of life were found by investigators to have a 0.50 RR of being sensitized to dogs at age 18 years compared with those who did not have an indoor dog during the first year (95% CI, 0.27-0.92). Males and females born by cesarean section had a 0.33 RR of sensitization (95% CI, 0.07-0.97).
Regarding differences in sensitization according to delivery type, the researchers wrote that “exposure to the vaginal microbial environment during normal delivery [might] result in microbial stimulation of the innate immune system or colonization of the respiratory and gastrointestinal tract with diverse bacteria being ‘protective’ against subsequent development of allergies.”
Those with an indoor cat in the first year of life had less risk of being sensitized to cats (RR=0.52, 95% CI, 0.31-0.90). The researchers found that neither cumulative exposure nor exposure at any other age was related to either outcome.
“In our data, only exposure in the first year was associated with decreased risk of sensitization,” the investigators wrote. “This argues for the importance of the timing of the exposure with respect to some of the discrepancies in the literature involving studies in which the timing of animal exposures was not precisely defined.”
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This study by Wegienka and colleagues doesn't convince me that highly atopic parents should bring cats and/or dogs into the home when a newborn comes home from the hospital.
The authors do not have data as regard to exposure into late teens, ie, could their results be related to less exposure as they became older? The data has too many variables, ie, why was dog exposure in first year of life only protective for males and the cat data was only positive in children who had a parental history of allergy?
—Gary S. Rachelefsky, MD
Infectious
Diseases in Children Editorial Board member
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