Dogs may prime baby’s immunities

Published 9:00 pm Monday, February 9, 2004

It’s been accepted for years that house pets were not good for children with asthma and allergies. But a newer theory, strengthened by the latest study, suggests otherwise.

The new study found that infants with certain forms of a gene that is a marker for immune function, who also have a dog, are much less likely to develop allergic skin rashes, a sign that their immune systems are stronger than those who have not had a dog in their lives.

And it may not be the dog, but the dirt that dogs track in.

"Having a dog was associated with a particular pattern of immune system development," said Dr. James Gern, a pediatric allergist at the University of Wisconsin in Madison. He and his team tracked 285 children from birth to age 5. Those without a dog during the first year of life were twice as likely to have an unexplained skin rash than those with a dog.

The hygiene hypothesis suggests that dirt primes the immune system and helps infants develop a stronger immune response. The findings appear this month in the Journal of Allergy and Clinical Immunology.

The Wisconsin study also provides the first evidence that certain genes could increase or decrease the risk for allergy and asthma — and having a dog could influence the outcome. In this study, they collaborated with Carole Ober of the University of Chicago to look at a marker of immune function, a gene called CD14.

Kids in houses with dogs had more immune system stimulation, measured by CD14, and less dermatitis, which many doctors believe is an early sign of allergy. But only two varieties of CD14 (CD14-TT and CD14-CT) were associated with less risk of dermatitis if a dog were present. Those with the third form, CD14-CC, were not affected by the presence of a dog.