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BOSTON -- Children whose mothers had a dog while they were pregnant were significantly less likely to develop atopic dermatitis, or eczema, as toddlers, a researcher here found.

At age 2, children with prenatal dog exposure had a significant reduced risk of eczema compared to children whose mothers were not exposed to dogs (OR 0.48, 95% CI 0.30-0.76, P=0.002), reported Gagandeep Cheema, MD, of Henry Ford Hospital in Detroit, and colleagues.

But the significance of this effect did not extend into older childhood. The reduced risk of eczema for children with prenatal dog exposure only trended towards persistence of this effect at age 10, but was still non-significant (OR 0.62, 95% CI 0.37-1.05, P=0.077).

At a at the American College of Allergy, Asthma & Immunology annual meeting, Cheema said that prior research has found that exposure to dogs during infancy is linked with a lower risk of eczema in early childhood, but it was unclear if this effect persists into late childhood.

"Children with eczema can also develop asthma, allergic rhinitis and food allergies, so we thought it was important to look at potential modifiable risk factors," she said.

Jay Portnoy, MD, of Children's Mercy Hospital in Kansas City, Missouri, who was not involved with the study, said that early dog exposure associated with a lower risk of eczema has been suspected for a long time, but "this study confirms it and is large enough to provide confidence in the results."

"Families with allergies shouldn't necessarily get dogs if they don't like them, but if they are 'dog people' they should not avoid getting one due to family history of allergies. But it could really be man's best friend," Portnoy told 番茄社区app.

Cheema and colleagues examined data from 794 maternal-child pairs in the Wayne County Health Environment Allergy and Asthma Longitudinal Study (WHEALS) cohort. These pairs were included if a prenatal interview was completed and they attended one of two study-related clinic visits at age 2 or 10. Eczema was determined by a physician through patient history and physical examination, and dog exposure was defined as maternal report of keeping "one or more dogs indoors for at least one hour daily during pregnancy" for at least 2 weeks.

Overall, 60% of participants were African American, and a little over a third delivered via cesarean section. About a quarter reported having prenatal indoor dog exposure. A little over half of patients were atopic at age 2.

Among participants with atopic dermatitis, researchers also examined early, late and persistent eczema. Children with prenatal dog exposure had significantly lower odds of developing early eczema, or a diagnosis of eczema at age 2, but not age 10 (OR 0.32, 95% CI 0.14-0.74, P=0.008) and persistent eczema, or eczema at both ages 2 and 10 (OR 0.36, 95% CI 0.15-0.88, P=0.026).

Cheema noted that these associations were largely unaffected when adjusted for a variety of confounders, including maternal eczema, race, mode of delivery and first born child.

She said that the mechanism for the protective effect of prenatal dog exposure on a child developing eczema remains elusive, but hypothesized that dogs have the potential to alter the developing infant microbiome and "skew away from the Th2 pathway."

Cheema said that because dysbiosis plays a role in the disease process of eczema, her group is now looking at research related to the gut microbiome.

"We're hoping to possibly identify phenotypes associated with certain exposures, to give us a more specific underlying reason for the protective effect of indoor dog exposure," she said.

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