CNN.COM / HEALTH
August 28, 2002 Posted: 5:39 AM EDT (0939 GMT)
By Gina Greene - CNN
(CNN) -- Flying in the face of conventional wisdom, a new study shows that children who grow up with pets in the home have a reduced risk of developing common allergies. "It was very strongly the opposite of what we expected to find," said lead researcher Dr. Dennis R. Ownby, who is chief of allergy and immunology at the Medical College of Georgia in Augusta. "Allergists have been trained for generations that dogs and cats in the house were bad because they increased the risk of you becoming allergic to them; we know that before you become allergic to something you have to be repeatedly exposed to it."
But the study, released in Wednesday's Journal of the American Medical Association -- which tracked a group of 474 babies from birth to about age 7 -- found differently. Researchers found that the 184 children in the group exposed to two or more dogs or cats in infancy were half as likely to develop common allergies than the 220 children who had no pets in the home.
The researchers found the group exposed to animals had fewer positive skin test to indoor allergens -- such as pet and dust mite allergens -- and also outdoor allergens like ragweed and grass. Moreover, the kids exposed to cats and dogs were almost half as likely to have hyper-responsive and easily irritated airways -- a risk factor for asthma.
The research also suggests that more is better. For example, 15.5 percent of kids without pets were allergic to cats compared with almost 12 percent with one cat or dog. That number dropped to just under eight percent when two or more pets were in the home. "This contributes to the mounting evidence that the things allergists have believed for years and parents have lived by are wrong," said Ownby, Indeed the body of evidence is growing. In fact, a recent study sponsored by the National Institute of Allergy and Infectious Diseases found that low-to-moderate amounts of cat allergen triggered allergies in children while high amounts had a preventive effect against allergies -- and asthma as well.
So what is it about cats and dogs? Researchers think the secret may lie in endotoxins, the breakdown products of bacteria found in the animals' mouths. They're thought to force the body's immune system into developing a response pattern that's less likely to lead to allergic reactions.
"The bottom line," says Ownby, "is that maybe part of the reason we have so many children with allergies and asthma is we live too clean a life.