Early Exposure to Pets May Put Leash on Allergies

Exposure to at least two dogs or cats in the first year of life may drastically reduce the risk of allergies, including reactions to molds, grasses and pollen, scientists report in an unusual line of research published last week.

The team of Georgia scientists pursuing this seemingly offbeat path of research says it now has some fairly solid leads on how animals help ward off allergies, including those known to trigger asthma.

“We started this research almost 14 years ago, looking at all of the factors that cause allergies,” said Dr. Dennis Ownby, a professor of pediatrics and medicine at the Medical College of Georgia in Atlanta.

Ownby and his team report the results of their investigation in the Aug. 28 issue of the Journal of the American Medical Assn. In the study, allergies--or the lack of them--were studied in nearly 500 healthy children born between April 15, 1987 and Aug. 31, 1989.

A key in the research was to pinpoint the amount of exposure children had by age 1 to cats and dogs, the most common house pets. Those with exposure to at least two dogs or cats had a 75% lower risk of allergies. The study found that just one pet didn’t confer protection.

Ownby theorizes that exposure to the protein byproducts of a certain class of bacteria known as gram-negative explains why some children have such a dramatically lower risk of serious allergies. Gram-negative bacteria include E. coli and other organisms that can be found in animal feces.

Pets lick themselves and spread the byproduct of the bacteria on their fur. Bacterial byproducts are transferred to children who pet, kiss or hug the animals, Ownby said.

“We think that something related to the cat/dog exposure forces the immune system away from the predisposition to allergic reactions,” Ownby said. Such exposure, he added, also minimizes the effects of other potential allergens, such as molds, pollens and grass. Prior studies in Europe showed that children who grew up on farms and were in the constant presence of animals tended to have fewer allergies.

Dr. Marianne Frieri, director of allergy and immunology at Nassau University Medical Center in East Meadow, said that although the premise of the study is intriguing, more research needs to be done.

“I am very much aware of the paradoxical effect here,” said Frieri, referring to animals as a source of protection, especially in the face of medicine’s long-standing insistence on shooing animals away from allergic children.

“I don’t want anyone to get the notion that they can now go out and buy 10 cats,” Frieri said. “The issue here is exposure in the first year of life.”

Experts agree that the new study provides a foundation to move an esoteric scientific notion called the hygiene hypothesis from a good idea into provable theory. The decade-old hypothesis suggests that modern environments have become “too clean.”

According to the theory, the immune system, primed throughout evolution to fight scourges since eliminated by antibiotics and vaccines, now like a turncoat responds with allergies and asthma.

“It has only been within the past few years that we have seen a few well-designed studies that begin to fit [the hygiene hypothesis]. We think ours is one,” Ownby said.