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MONDAY, March 22 (HealthDayNews) -- Family pets appear to protect infants from developing allergies, but only in homes that are free of cigarette smoke, researchers report.

While children of non-smoking parents were half as likely to develop allergies if exposed to pets in the home, researchers found the presence of pets "did not significantly alter the risk" if one or both parents smoked at home.

Although exact causes remain unclear, "inflammation in the airways caused by the particles and chemicals in cigarette smoke may be just as bad and block the effects, whatever they are, of being exposed to the dog or the cat," says study author Dr. Dennis Ownby, of the Medical College of Georgia in Augusta.

He presented his findings March 22 at the annual meeting of the American Academy of Asthma, Allergy & Immunology (AAAAI), in San Francisco.

Sensitivity to cat or dog dander remains one of the most common forms of allergy, and parents of newborns have long been concerned that the presence of animals in the home might encourage allergies in newborns. However, a string of studies released over the past few years seems to support the opposite view -- that early exposure to cats or dogs actually helps babies avoid a wide range of allergies.

"During that early, early time there seems to be some protection," says AAAAI spokeswoman Dr. Linda Ford. "I don't worry if women are pregnant and they are bringing a child into the house and they have an animal, cat or dog."

However, a quarter of adult Americans still smoke, and Ownby says he wanted to "take into account whether kids are getting exposed to cigarette smoke" at home, along with their exposure to pets.

In their study, the researchers examined the home environment and allergy histories of 474 Detroit-area children from birth to 7 years of age.

As expected, they found the presence of dogs and cats in non-smoking homes during infancy cut children's risk for allergy to dander, ragweed, dust mites and other agents by about 50 percent, compared to homes without pets.

However, no significant reduction in allergies was observed in homes contaminated by secondhand smoke -- even in the presence of pets.

The findings should give parents yet another reason to 'butt out' for good, Ownby says, for their own health as well as the health of their children.

Besides increasing allergy risk, "being exposed to smoke greatly increases the amount of trouble a child will have with their asthma," Ownby points out. "And being exposed to cigarette smoke also increases the risk that a child will have recurrent ear infections, and pneumonia severe enough to require admission to a hospital. There are a whole host of bad effects of secondhand cigarette smoke."

On the other hand, new parents should rest easy when it comes to keeping Fido or Fluffy around. "I don't think they have to feel guilty about having a pet in terms of increasing risks to their children of having allergies," Ownby says.

The findings do not apply to older children with pre-existing allergies, however. "If you have a young child who's already having symptoms and they have a skin test and test positive for cat and dog, then that's a different story," Ford says. In such cases, "the cat or dog has got to go."

More information

For information on allergies and allergy control, visit the American Academy of Allergy, Asthma & Immunology. For help with quitting smoking, check with the American Lung Association.

(SOURCES: Dennis Ownby, M.D., Medical College of Georgia, Augusta; Linda Ford, M.D., spokeswoman, Academy of Asthma, Allergy & Immunology, and past president, American Lung Association; March 22, 2004, presentation, annual meeting, American Academy of Allergy, Asthma & Immunology, San Francisco)

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