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Family pets may prevent allergies

By Julia Sommerfeld

Aug. 27 —  Dogs may be more than man’s best friend — they may be baby’s, too. Growing up in a house with two or more cats and dogs appears to slash an infant’s risk of developing allergies later on, new research finds.

“CONTRARY to what doctors have been told for at least the past 30 years, being exposed to dogs and cats doesn’t increase the likelihood you will be allergic to them — it actually reduces the risk,” said study lead author Dr. Dennis Ownby, head of allergy and immunology at the Medical College of Georgia in Augusta.
       Even more unexpected, he said, was his finding that having pets in the first year of life also reduces the risk a child will later have allergic reactions to other common culprits such as dust mites, grasses, pollen and mold.
       Earlier studies on the connection between pet exposure and allergies have been mixed.

 In the new study of more than 400 Detroit-area children, those who had two or more dogs or cats in their first year of life were 50 percent less likely to have allergies between the ages of 6 and 7 than kids with no pets. Exposure to just one pet, however, didn’t offer much of a protective effect.
       But this doesn’t mean parents should bring home the pound, stressed Dr. David Stempel, an allergist and clinical associate professor of pediatrics at the University of Washington at Seattle. “Based on this study, I wouldn’t recommend getting a lot of dogs and cats to prevent allergies yet. Plus, the general recommendation to not have cats or dogs in an already allergic family still stands — why put the health of allergic parents at risk?”

 Ownby agrees, but says the message of the study is really, “If a family already has pets in the home and the wife is expecting a child, this study means you don’t have to rush out and get rid of the pet.”

 Ownby said he doesn’t know exactly why having multiple pets makes kids tolerant to a variety of allergens, but said the study further supports the “dirt is good” hypothesis. The popular theory holds that exposing a young child to animal dander, dust mites, other allergens and germs helps the immune system build tolerance to them.
       The study, which appears in Wednesday’s Journal of the American Medical Association, tracked 474 healthy infants born between 1987 and 1989 in suburban Detroit. The children were followed from birth until they were up to 7 years old.

When the children were between 6 and 7, researchers gave them skin prick tests for dog, cat, dust mites, ragweed and blue grass allergies.
       Around 34 percent of kids who had no pets or one pet during their first year of life showed allergic sensitivity to at least one of the skin prick tests. But only 15 percent of youngsters who had been exposed to two more cats or dogs showed any allergic responses.
       The children also underwent blood tests for antibodies known as immunoglobulin E, or IgE, that indicate allergic response. Positive blood tests for at least one allergen-specific IgE antibody were seen in nearly 39 percent of kids with no pets, 41 percent of those with one pet and just 18 percent of the children with exposure to at least two cats or dogs.

After taking into account possible confounding factors such as parental allergies and smoking, dust levels in the house and exposure to pets after the first year of life, researchers found the children with two or more pets as infants had a 77 percent lower risk of having a positive skin prick test and 67 percent reduced risk of a positive blood test compared to kids with no pet in their first year.
       “This opens up an exciting area of research — if we understand how the immune system controls this response we can identify and immunize people not to be allergic,” said Dr. Thomas Platts-Mills, head of allergy and asthma at the University of Virginia in Charlottesville, who wrote an editorial commenting on the study.
       There’s a strong association between risk of allergies and asthma in children. So if you decrease risk of allergy you very likely will reduce risk of asthma, which is considered a major health problem among U.S. kids, said Ownby.

 But asthma testing showed a reduced risk of the breathing disorder only in boys, with male children who had two or more pets significantly less likely to show signs of airway constriction or wheezing than their pet-less counterparts.
       Ownby said this suggests the immune system is developing differently in boys and girls.
       Stempel, however, calls the gender disparity “puzzling.”
       “At this age, the development of asthma is pretty gender neutral. I don’t understand immunologically why there would be a difference,” he said, adding that further research is needed.

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