In his recent study, Gern analyzed the blood of babies immediately after birth and one year later. He was looking for evidence of an allergic reaction, immunity changes, and for reactions to bacteria in the environment.
If a dog lived in the home, infants were less likely to show evidence of pet allergies -- 19% vs. 33%. They also were less likely to have eczema, a common allergy skin condition that causes red patches and itching. In addition, they had higher levels of some immune system chemicals -- a sign of stronger immune system activation.
"Dogs are dirty animals, and this suggests that babies who have greater exposure to dirt and allergens have a stronger immune system," Gern says.