A team of researchers from Japan has found that children exposed to pet cats or indoor dogs during fetal development or early infancy appear to develop fewer food allergies, compared to other children.
Food allergies have been on the rise over the last few decades, with over 32 million Americans having a life-threatening food allergy, according to Food Allergy Research & Education (FARE). An allergy comes from an adverse immune response when exposed to a given food type. The allergic reaction involves the immune system attacking food proteins that are normally harmless, and can lead to anaphylaxis in serious cases.
The idea that exposure to pets is effective in preventing allergic disease has been suggested for some time. Research into the “hygiene hypothesis” – the idea that extremely clean environments actually fail to provide sufficient exposure to germs needed to prime our immune systems to fight infections – has shown the potential benefits of being exposed to dogs during early infancy, especially in association with food allergies. However, less research has been conducted on exposure to other pets.
This latest study sought to address this. Hisao Okabe, a researcher from the Fukushima Regional Center for the Japan Environment and Children’s Study, Japan, and colleagues examined data on pet exposure and food allergies for 66,215 children to see if contact with different animals impacted the risk of food allergies.
The information was drawn from the Japan Environment and Children’s Study, an ongoing nationwide, prospective birth cohort study that included 97,413 mothers and their children. According to the data, around 22 percent of the children studied had been exposed to pets during the fetal period, and mostly to indoor dogs and cats.
The information was transcribed from medical records during the first trimester, at delivery, and at the one-month check-up. After delivery, additional information was collected every six months from caregivers, who carried out self-reported questionnaires. As such, the quality of this information was contingent on the accurate recall of each participant. Moreover, the team was not able to individually assess the child participants for their reported allergies, which meant they relied on the parent-reported doctor’s diagnosis obtained from the questionnaires. This was because methods used to test for food allergies, particularly oral food challenge – a validated form of allergy diagnosis – carry the risk of inducing anaphylaxis and would not be suitable for a cohort as large as the study population.
The team’s findings suggest that exposure to indoor dogs and cats significantly reduced the incidence of food allergies. Such exposure to indoor dogs, they found, significantly lowered the likelihood of developing allergies to milk, eggs, and nuts. Exposure to cats significantly lowered the chances of developing allergies to eggs, wheat, and soybeans.
The results did not reveal any significant difference for children living with outdoor dogs – but, unexpectedly, they found that children exposed to hamsters had a much higher risk of nut allergies. This, they believe, may be because hamsters eat nuts in abundance. If they are correct, it suggests that nut allergens could be communicated to infants through skin exposure, a process called “percutaneous sensitization”, to hamsters or house dust. “Therefore”, the authors argued, “family hand washing and keeping hamsters away from babies might minimize the risk of nut allergy even if hamsters are kept as pets.”
According to the authors, the study demonstrates the potential benefits of having dogs and cats as pets when children are very young. These results, they claim “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.”
Although the results do not necessarily demonstrate a causal relationship, they nevertheless help guide future research into the mechanism associated with childhood food allergies.
The study was published in Plos One.