By Dr. Becker
In the last dozen years, numerous studies have emerged that suggest children who grow up with a dog or cat are less likely to develop allergies, asthma, and respiratory and ear infections than children without pets.
- In a 2012 study published in the journal Pediatrics,1 researchers showed that infants who had contact with dogs in the home had 31 percent fewer respiratory tract illnesses and infections, 44 percent fewer ear infections, and 29 percent fewer antibiotic prescriptions than kids with no contact with dogs.
- A study published in 2011 in the journal Clinical & Experimental Allergy2 showed that infants living in homes with cats have 50 percent fewer cat allergies than children not exposed to kitties from birth to one year of age.
- A 2009 study published in The Journal of Allergy and Clinical Immunology3 showed that kids who lived with both a cat and a dog were less likely than other children to have allergies at age 13.
- A 2008 study published in the journal Clinical & Experimental Allergy4 concluded that exposure to dogs in infancy – especially around the time of birth – is associated with changes in immune development and a reduction in wheezing and allergic hypersensitivity.
- A study published in 2002 in the Journal of the American Medical Association5 showed that infants exposed to two or more dogs or cats during their first year had fewer allergies not only to pets, but also to dust mites and ragweed.
The Protective Power of Dog Dust
Up until now, scientists have been unable to pinpoint exactly what the protective mechanism is, but have speculated it is related to the hygiene hypothesis. The hygiene hypothesis holds that our modern lifestyles are actually too sanitary for our own good. Our immune systems aren’t being exposed to enough pathogens (bacteria, viruses, and parasites) to learn to do their jobs effectively.
Recently, a group of researchers at the University of Michigan conducted a study6 that provides exciting new insight into the question of why pets in the home often result in children with better functioning immune systems.
The study involved three groups of mice. The first group was exposed to dust collected from the home of a dog owner. The second group was exposed to dust from a non-dog household, and the third group was not exposed to any dust.
The scientists then exposed all three groups of mice to two asthma-related allergens. The mice that had been exposed to dog dust had much less inflammation in their airways and produced less mucus than the other two groups of mice.
The Secret Weapon? Microbes Living in Dog Dust
It wasn’t actually the dog dust that was protective, however. It was what was living in the dust – microbes (bacteria). The researchers found that a single bacteria, Lactobacillus johnsonii, was in ample supply in the guts of the group of mice exposed to the dog-related dust. The microbes actually reshaped the community of living organisms in the rodents’ GI tract, and these changes affected the immune response of the mice and their ability to fight off certain allergens.
The researchers gave a live form of the L. johnsonii bacteria to the two groups of mice not exposed to dog dust, and those animals also developed protection against airway allergen challenge and viral respiratory infection.
The researchers concluded, “The study identifies L. johnsonii as a pivotal species within the gastrointestinal tract capable of influencing adaptive immunity at remote mucosal surfaces in a manner that is protective against a variety of respiratory insults.”
According to Time, study results could lead to additional research into enhancing gut bacteria in children as a way to protect them from allergies and asthma.