Children raised with pets less likely to be allergic

New study overturns conventional thinking on animal, pollen allergies

August 28, 2002|By Jonathan Bor | Jonathan Bor,SUN STAFF

The truth about cat and dog allergies might be the opposite of what experts have long suspected, according to a new study. Raising children alongside the furry companions might reduce rather than increase the likelihood that they will break out in itching and sneezing fits.

Not only that, but the study of 474 youngsters in suburban Detroit found that those raised from birth in households with two or more cats or dogs were also less likely to develop allergies to pollen, mold and grasses.

The finding, published in today's edition of The Journal of the American Medical Association, clashes with conventional wisdom about pet allergies, which holds that children are more likely to develop reactions the more they are exposed to the animals.

"For 30 years, physicians in general have been taught that early exposure to cats and dogs is more likely to increase the risk that a child will develop an allergy to cats and dogs," said Dr. Dennis Ownby, an allergist with the Medical College of Georgia, who directed the study. "What we found was just the opposite."

The finding, although preliminary, suggests that an early dose of dog or cat dander might somehow tweak the immune system in a way that keeps it from mounting the exaggerated response to irritants that can cause allergic symptoms.

Evidence from this and other recent studies should come as a relief to pet-loving parents who wondered whether they should kick their animals out of the house before bringing a child into the world, Ownby said.

"There are many different factors a family has to consider," Ownby said, including a pet's cost and the risk of animal bites, "but I think pets in the home may have a clear beneficial effect in terms of reducing the allergy risk."

Ownby and others familiar with the study cautioned that it does nothing to erase the notion, backed up by years of observation, that parents whose children do suffer from dog or cat allergies ought to remove the offending animals.

"Once children are allergic, the animals can only do harm, and typically the children will only get worse," said Dr. Robert A. Wood, a researcher at the Johns Hopkins School of Medicine.

In the Detroit study, doctors who followed children in the first six years of their lives found those who were raised with two or more animals were 70 percent less likely to become allergic than other children.

Substantially lower rates of allergies to other irritants were also noticed in the pet-keeping households.

Larger and longer studies are needed before doctors can conclude that pets offer any kind of long-lasting allergy protection to humans, Ownby said. Also, the children in the study were overwhelmingly white, so the findings cannot be generalized to African-American and other minority children.

The findings, however, are not without precedent.

Studies in the United States and New Zealand have recently produced similar evidence. Scientists studying farming communities in Europe also have found that children exposed early in life to livestock suffer less from allergies and asthma.

Dr. Thomas A.E. Platts-Mills, a researcher with the University of Virginia Health Sciences Center who has conducted some of the studies, said yesterday that for many years scientists have ignored compelling evidence that animals - unlike other sources of itching and sneezing - might actually protect people.

"People investigating allergy were extremely blind to this for years," said Platts-Mills, author of an editorial in this week's JAMA.

His own studies, for instance, showed that people in cat-loving societies such as New Zealand are exposed to much higher concentrations of airborne cat allergens than of dust mites. "Yet cat allergy is present in 6 percent to 10 percent of the population, and mite allergy goes up to 30 percent," he said.

Ownby said it is far too soon to explain the phenomenon, but he suggested that the explanation might lie in bacteria that animals carry on their fur and paws.

The bacteria release molecules called endotoxins, which might shift the immune system into a healthier balance.

A less likely explanation, he said, is that the sudden jolt of allergen from a few pets is capable of priming an infant's immune system.

"Instead of forming antibodies that cause allergy, you form a different class of antibodies that don't allow an allergic reaction to happen," he said.

Bringing a pet into the home is one of the few ways to significantly boost a person's exposure to allergens, he said. It can produce as much as a 100-fold increase in the amount of airborne allergen.

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