Having a pet in the household makes it less likely young children will develop severe food allergies. Now, experts are beginning to understand why.
In other words, kids, here's the proof you need to show your parents why you really do need a dog.
"It's been known for a while... [there's] a lot of epidemiological evidence that people who have pets seem to have less allergies, less asthma, less atopic dermatitis," says Krishna Roskin, associate professor of biomedical informatics at Cincinnati Children's and a corresponding author on a recently published study.
Roskin and a team of 19 experts in asthma, biomedical informatics, genetics, and immunology discovered that children with food allergen sensitivities — think kids who are allergic to eggs, peanuts, or milk — have B cells in their immune systems that produce high amounts of an antibody called IgE that drives severe allergic reactions.
"The immune systems of kids with food sensitization seem to be about three years behind their peers in the development of their IgE B cells," Roskin tells WVXU. "Having a dog seems to counteract that."
The findings were published online Nov. 11 in the journal Allergy.
The team analyzed the genetic activity of antibodies produced by 147 children under six years old with atopic dermatitis. That's a skin condition that increases a child’s risk of later developing severe allergic disease. They looked for signs of an immune process known as somatic hypermutation. That process pushes B cells into the immune system, causing more intense immune reactions.
Unexpectedly, they found children with food allergen sensitivities actually had less somatic hypermutation of IgE genes.
"At least for children in this cohort, under six years old, food allergic sensitization looks more like a suppressed immune system instead of an overactive one, as most immunologist would naturally assume,” says Roskin. "The developing immune system of young children with food sensitivities seems to lag behind other children by over three years."
However, having a dog, researchers found, appears to restore normal IgE immune development.
The benefits do appear to be best earlier in life while a child's immune system is learning and ramping up. One hypothesis about why dogs are so advantageous is called the hygiene theory. Simply put, our homes are too clean — dogs go outside and track in dirt and other things that help build the desired immune response. Less sterile environments have a positive effect on developing immune systems.
It's unclear if cats are as beneficial as dogs.
"We make a comment that we don't see a pattern for cats, but we don't really have a lot of cats in the study, so we can't quite dismiss cats completely," Roskin adds. "Other studies have found that dogs and cats are very different. Cats are very fastidious; they don't tend to go outside and get dirt all over their skin. And there's differences in the antigens that cats have versus what dogs have."
The study was conducted using data from the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children (M-PAACH) cohort. It's one of the largest such cohorts in the world, and the first U.S.-based prospective infant cohort.
The study's findings show the B cell changes were only related to food allergies. The same response was not connected to other allergies like plant pollens or molds.
Read more:
