Respiratory outcomes among inner-city children with asthma may be linked to both dog allergen exposure and dog-associated nonallergen exposures, according to an analysis published in Pediatric Allergy and Immunology.
To examine this theory, researchers performed a secondary data analysis from the DISCOVER (Domestic Indoor Particulate Matter and Childhood Asthma Morbidity) longitudinal observational cohort study, originally conducted among inner-city children in Baltimore, Maryland. The study included both dog allergen and the presence of dogs as exposures.
A total of 162 children aged 5 to 12 years with physician-diagnosed asthma were recruited between January 2009 and February 2015. All participants were evaluated at baseline and at 3, 6, and 9 months. At each of the follow-up visits, the investigators assessed patients’ respiratory outcomes, such as fractional nitric oxide concentration in exhaled breath and pediatric asthma diary, along with the home environment, including dog allergen concentrations and presence of a dog. At baseline, allergy testing was performed to establish the patient’s sensitization status via use of percutaneous skin testing or immunoglobulin E testing.
A total of 65.4% of the DISCOVER participants had persistent asthma. Overall, the baseline prevalence of observed dog presence was reported to be 36.0%. The baseline distribution and prevalence of dog allergen exposures were 0.08 µg/g and 9.88%, respectively, for bedroom; 0.04 µg/g and 8.13%, respectively, for bedroom floor; and 0.0 µg/g and 11.88%, respectively, for kitchen. The investigators stratified the population into 4 categories, based on both dichotomous allergen exposure status at different sites (eg, bed) and dog-specific sensitization status, to examine the effect of allergen exposures, as well as the interaction between allergen exposures and sensitization to specific allergens on respiratory outcomes.
Results demonstrated that dog allergen exposure was highly associated with worse respiratory outcomes, regardless of where the dust had been collected. The interaction between sensitization and exposure to dog allergen, however, was not statistically significant across all outcomes and all locations.
When the effects of dog presence and dog allergen exposure on asthma morbidity were stratified according to specific sensitization status, dog presence was not significantly associated with worse respiratory outcomes, regardless of allergic sensitization status. When dog allergen was considered, however, dog-associated nonallergen exposures stemming from the residual effect of dog presence became linked to lower odds of absence from school and symptoms of nocturnal asthma among dog-sensitized youth.
“The intriguing find that dog-associated non-allergen exposures may be associated with lower asthma morbidity after controlling for the deleterious effects from allergen exposure is biologically plausible,” the researchers wrote. “There is growing evidence that animal microbiota and endotoxin may exert immunomodulatory effects on the development of or progression of atopic diseases via associated cytokines and metabolites.”
Additional studies are warranted to explore how dog allergen exposures affect asthma morbidity among nonsensitized patients.
Tsou P-Y, McCormack MC, Matsui EC, et al. The effect of dog allergen exposure on asthma morbidity among inner-city children with asthma [published online October 25, 2019]. Pediatr Allergy Immunol. doi:10.1111/pai.13144