Dr. James Gern of the University of Wisconsin-Madison studied 101 children who lived with a dog in the house and 84 who were raised with a cat in the house. In all cases, either the child’s mother or father had allergies or asthma.

The children who lived with a dog in the house had less eczema, which often is a precursor to allergies and asthma. They were also less likely to develop a specific allergy protein and showed higher levels protective substances that help the body resist allergic reactions.

Those children living with cats showed no lowered allergy risk at all.

The explanation? Dirt. Gern says that early exposure to dirt tends to jump start the immune system in children. Since dogs tend to be dirtier than cats, they offer better exposure to dirt.

“Dogs are larger, and are more likely to lick you in the face compared to cats,” said Gern.