Prior research indicates an association between prenatal pet exposure and immunoglobulin E (IgE) trajectory through age 2. To determine if this association persists during ages 10-14, researchers assessed data on a cohort of 1,193 mother-child pairs in southeast Michigan. The study team found that the area under the curve for IgE levels during ages 10-14 was 28.8% lower in children with prenatal pet exposure when compared with those with no such exposure. Dog ownership, associated with a 26.7% lower IgE trajectory, was the main driver of this association, with cat ownership having no significant association with IgE trajectory. The findings support the “hygiene hypothesis,” said Jay Portnoy, MD—who was not involved in the study, in a statement—which is based on dogs being particular carriers of bacteria from outside into the home and resulting in a potential influence on a child’s microbiome early in develop. The hypothesis is supported by previous studies suggesting an association between dog ownership and reduced risk of eczema in children. Race/Ethnicity and delivery method affected the association between pet exposure and IgE reductions, with children of African-American mothers experiencing an 11.3% reduction versus a 33.6% reduction in other races and ethnicities, and children delivered via cesarean delivery experiencing a 46.2% lower IgE trajectory versus an 18.1% lower trajectory in children delivered vaginally.