Early Exposure to Pets and Pet Allergies

The Detroit Childhood Allergy Study included 566 children who were enrolled as infants. Families reported current pet owning at annual interviews from infancy through age six. At annual interviews, families were asked, “Have you had any pets in your home for more than two weeks?” The time period two weeks was used to differentiate between household pets and those in the home on a temporary basis. Families were also questioned about the number of hours per day the pet or pets were kept indoors. The introduction to the study report stated, “Consistent with the hygiene hypothesis, we postulated that enhanced microbial exposure due to increased richness, evenness, and diversity of the home microbiome, could bias the immune system away from a Th2-like response, potentially through stimulation of innate immune receptors, resulting in lowered risk of allergic sensitization to common allergens.”(1)

According to the American Academy of Allergy, Asthma, & Immunology, the hygiene hypothesis suggests that children who are not exposed to germs develop immune systems not trained to tell the difference between harmless and harmful irritants. “This concept is supported by studies that show that individuals living on farms develop fewer allergic diseases. The theory is that farm animals increase exposure to germs and germ components called endotoxin. These endotoxins stimulate the immune response and decrease allergic inflammation.”(2)

A majority of the subjects with pets in the home during the first year of life had a reduced risk of allergies, the study found. Boys and girls who had a cat during the first year of life had half the risk of a cat allergy. Boys with a dog at home during the first year of life had half the risk of a dog allergy. The study concluded: “The first year of life is the critical period during childhood when indoor exposure to dogs or cats influences sensitization to these animals.”(1)


(1) Wegienka, G. PhD, Johnson, C. PhD, et. al., Clinical and Experimental Allergy, Lifetime Dog and Cat Specific Sensitization at Age 18 Years, https://www.ncbi.nlm.nih.gov/
(2) American Academy of Allergy, Asthma, & Immunology, Increasing Rates of Allergies and Asthma, https://www.aaaai.org/