Study Links Early Pet Exposure, Reduced Food Allergy Incidence in Japanese Children

A study published in PLoS One found that exposure to pets during fetal development or early infancy was associated with reduced instances of food allergies in young children, with different pet exposures potentially reducing the incidence risk of certain allergen types.

“The hygiene hypothesis suggests that pet exposure is effective in preventing allergic disease, and some studies have reported the beneficial effects of dog exposure during fetal development or early infancy on food allergy,” the authors wrote. “However, the effects of exposure to pets other than dogs on the kinds of food allergies remains unaddressed.”

The study explored pet exposure and food allergies using data from the Japan Environment and Children’s Study, a national study including 97,413 mothers and their children. The aim was to identify associations between exposure to variety of pet species during fetal development or infancy and the risk of a variety of food allergies.

A total of 66,215 full-term and single-birth children were included in the study, all of whom had data on covariates, pets, and food allergies through 3 years of age available. Of the children included in the study cohort, 21.6% were exposed to pets during the fetal period. Logistic regressions for each pet species, causative food, and exposure timing were conducted.

Children who were exposed to dogs kept indoors or cats in the fetal period or early infancy demonstrated a reduced incidence risk of all food allergies until 3 years of age. The adjusted odds ratio (AOR) for food allergies was 0.86 (95% CI, 0.78-0.93) in children who had indoor dog exposure during fetal development and 0.87 (95% CI, 0.80-0.94) for children with dogs kept indoors during early infancy. After adjusting for covariates, outdoor dog exposure was not associated with reduced food allergy risk. The AOR was 0.84 (95% CI, 0.75-0.93) for children exposed to cats during fetal development and 0.87 (95% CI, 0.78-0.95) for those exposed to cats during early infancy.

In terms of specific food allergies, dog exposure was estimated to reduce the risk of egg, milk, and nut allergies. Exposure to cats, however, was estimated to reduce the risk of egg, wheat, and soybean allergies. On the other hand, exposure to hamsters during fetal development was estimated to increase the incidence risk of nut allergies among children in the cohort. Exposure to turtles and birds during fetal development was not found to be significantly associated with reduced incidence of food allergies.

Of the children in the study, 51,858 were in the non-exposure group, 1072 were exposed to pets during fetal development, 3129 in early infancy, and 10,156 were exposed to pets during both fetal development and infancy. An analysis of pet exposure timing estimated that children exposed during both fetal development and early infancy were at a reduced incidence risk of food allergies overall, but not children exposed during only 1 of the 2 life stages. The same was found for milk, wheat, and soybean allergy incidence. Egg allergy, however, was reduced when children were exposed in both stages and infancy alone, but not fetal development alone.

Nut allergies were not associated with dog or cat exposure at any time, and dog or cat exposure during fetal development alone was not significantly associated with the incidence risk of food allergies.

Overall, the study suggests that exposure to pets during fetal development and infancy may reduce the risk of food allergies in young children.

“We also demonstrated the benefits of maintaining dogs and cats after birth,” the authors wrote. “These findings reduce concerns about the development of allergic diseases caused by keeping dogs and cats. Reducing the incidence of food allergies will significantly reduce childhood mortality from anaphylaxis.”

The mechanisms behind the effects of pet exposure on allergy risk are not yet known, the authors noted. The study was limited in its observational nature and reliance on parent-reported doctor diagnoses in questionnaires. Further studies are needed to more accurately assess these associations, but the findings will inform the design of future trials.

Reference

Okabe H, Hashimoto K, Yamada M, et al. Associations between fetal or infancy pet exposure and food allergies: the Japan Environment and Children's Study. PLoS One. 2023;18(3):e0282725. doi:10.1371/journal.pone.0282725