Living with certain animals since fetal and early childhood development may bring extra benefits such as reduced risk of food allergies up to age 3, as a new study has found.
Published in PLOS One, was based on retrospective data from more than 66,000 Japanese minors. The results show that children exposed to cats and dogs at home see their risk reduced between 13 and 16% in relation to those who do not live with animals.
The species was linked to the different types of food. So, the exposure to dogs was associated with a lower incidence of allergies to eggs, milk and nuts —main food allergies— while contact with cats carried a lower incidence of allergies to eggs, wheat and soy.
Faced with this protection, living with hamsters was associated with nearly twice the risk of nut allergy. The researchers’ hypothesis suggests that these foods that serve as food for rodents can sensitize babies through physical contact or house dust.
The researchers further found that exposure to dogs or cats only during the fetal period had no significant effect on incidence. This finding suggests that continuing to keep these pets after birth may be beneficial in minimizing the chances of allergy.
“The results of this work support previous research indicating that certain environmental exposures, such as the fact that children growing up with an older sibling or in an agricultural setting for the first few years of life are associated with greater bacterial diversity and a lower risk of allergic sensitization,” says Sara Benedé Pérez, professor of immunoallergy at the Complutense University of Madrid in SMC Spain.
It is what is known as hygiene hypothesis. This theory, first proposed in 1989, proposes that the high incidence of allergies and autoimmune diseases in developed countries seems to be due to excessive sanitation that surrounds minors. Although not all scientists share this opinion.
While the study has not elucidated the mechanisms by which pet exposure affects food allergies, the authors theorize that could be related to the intestinal microbiota. “Exposure to pets may affect the infant’s gut microbiota directly or indirectly through changes in the parent’s gut microbiota or the household microbiome,” they write.
Continuing in this vein, a 2019 trial found that Babies raised on farms have more inflammation-fighting gut bacteria.
However, “it is a retrospective study, that is, existing data have been used to compare between two groups, allergic and non-allergic,” stresses Benedé.
The authors themselves acknowledge the limitations of this type of study when it comes to establishing a cause-effect relationship, explains the specialist, “since there are other uncontrolled factors that could influence the results, such as the genetic predisposition to suffer from some type of allergic condition or certain environmental factors”.
In any case, “the study raises an interesting question that needs to be further investigated and opens the way for designing research studies,” he says.
