NEW YORK (Reuters Health) - Young children who share their home with two dogs or cats in the first year of life are half as likely to become allergic to those animals than kids who grew up with only one dog or cat, or no pets, according to new study findings.

The finding flies in the face of advice given out by pediatricians and allergists for the last three decades, lead researcher Dr. Dennis R. Ownby of the Medical College of Georgia in Augusta noted in an interview with Reuters Health. Conventional wisdom has held that having a pet increases a child's risk of developing an allergy to that animal.

"Evidence is mounting that the opposite is true," Ownby said. He added that, "surprisingly," exposure to two dogs or cats also seems to cut the risk of developing other common allergies, such as sensitivity to dust mites and pollen.

While Ownby isn't calling for everyone with newborns to rush out and get two pets, he says the new findings should allow parents who already have pets to breathe a sigh of relief.

"These parents don't have to feel guilty that they are increasing their child's risk for allergies or asthma," he told Reuters Health.

In the current investigation, published in the August 28th issue of The Journal of the American Medical Association, Ownby and his team assessed the home environments of a group of 474 healthy children, starting at 1 year of age and continuing until they were 6 or 7 years old.

At the end of the study period, all of the children were tested for six common allergies: two type of house dust mites, dog, cat, ragweed and blue grass. Sensitivity was gauged by evaluating a child's skin reaction after he or she was given a skin prick test with the allergen.

Only 15.4% of the children with two cats or dogs in the house during the first year of life showed sensitivity to dogs or cats. The percentage of children with one dog or cat, or no pets, who had a positive skin test for dog or cat allergy was about 34%, the report indicates.

Kids who lived with two cats or dogs as infants were also half as likely to test positive for any one of the six common allergens compared with children with fewer or no pets, according to the researchers.

While allergies can be inherited, whether or not a child's parents had allergies did not influence the likelihood that the family would have pets, so this did not appear to be a factor in the findings.

The results support previous research that has found children growing up on farms, especially with farm animals, have fewer allergies, the authors note.

It is possible, Ownby explained, that increased exposure to common bacteria and their byproducts--called endotoxins--somehow causes the developing immune system to become less allergy-prone.

Most importantly, the researcher noted that the results suggest something in the environment can reduce the risk that allergies will develop. Further studies on the issue may help pinpoint what exactly that environmental element is, and help doctors to find a way to prevent children from developing allergies, he added.

Regardless of the current study findings, Ownby advises parents with known dog or cat allergies to steer clear of these pets. Allergies tend to run in families, he pointed out, and their children may already be allergic.

Commenting on the study, Dr. Thomas A. E. Platts-Mills of the University of Virginia Health Sciences Center in Charlottesville writes: "The new findings in relation to domestic animals provide an opportunity to understand the aspects of the allergic response that create risk for asthma; the mechanisms by which high exposure to foreign protein (i.e., the allergens in animal dander) can give rise to tolerance; and also, the factors that control the prevalence of allergic disease."

SOURCE: The Journal of the American Medical Association 2002;288:963-972.

Reference Source 89

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