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Avoiding Pets Won't Avert Allergies

Swedish study finds exposure may be a good thing

Please note: This article was published more than one year ago. The facts and conclusions presented may have since changed and may no longer be accurate. And "More information" links may no longer work. Questions about personal health should always be referred to a physician or other health care professional.

HealthDay Reporter

MONDAY, Oct. 20, 2003 (HealthDayNews) -- Contrary to commonly held beliefs, pet avoidance doesn't stop kids from developing allergies to animals, new research contends. In fact, exposure to pets might actually be a better hindrance, the researchers say.

A study of Swedish children found that while being allergic to cats was the most common airborne childhood allergy, keeping cats didn't necessarily increase the risk of developing allergies in 7-to-11-year- olds.

"Our research has found no increased risk of sensitization in children due to exposure to pets in the home," says study author Eva Rönmark. "Sensitization is genetic, and the big risk factor for getting it is if you already have it in your family." If that's the case, she adds, it's wiser not to keep pets in the home.

The joint Swedish-U.S. study found that children who had continuously owned cats or dogs actually developed less allergies to them than new pet owners, or those who had only been exposed earlier in life; among children who were allergic to cats, 80 percent had never kept a cat at home.

Rönmark, an allergy expert at the Department of Medicine at the Central Hospital of Norrbotten in Lulea-Boden, Sweden, and colleagues from the University of Virginia at Charlottesville conducted the research. They studied 2,454 children in Northern Sweden, 7 and 8 years old, on a yearly basis, and gave them skin sensitization tests every four years.

Parents were also asked to complete annual questionnaires on their children's risk factors.

"Parents need to be aware also, that just because you don't have a pet, your child won't develop sensitization," adds Rönmark. "Cat [and other] allergens can also be found where there are no cats -- for example, in schools, where they can be transferred by clothes."

The study found persistently high exposure to cat and dog allergens appeared to protect both boys and girls equally from developing allergies.

"If there are symptoms of sensitization, of course you should not keep the cat, and [that] can be sometimes difficult for kids," says Rönmark. "But at this time, though, we don't really know why these high exposure levels decrease the risks."

Researchers note that when a child with an existing allergy comes into contact with a cat or dog, naturally they begin to show more symptoms. Traditional thinking had been to assume that avoiding pets altogether would prevent these allergies.

The study suggests the new findings, published in the October issue of the Journal of Allergy and Clinical Immunology, are antithetical to the traditional views that exposure causes more severe symptoms.

"Studies we have done show that exposure to microorganisms has been shown to play a role in protecting against developing allergies," says medical researcher Marjan Kerkhof of the University of Groningen in the Netherlands. "And pets certainly would carry a lot of microorganisms."

"We've found that even during pregnancy, babies born to mothers who have pets in the house tend to have a lowered levels of IgE (immunoglobulins)," she says. "High IGEs have been shown to be a risk factor for developing allergies."

"But then," she cautions, "exposure to allergens seems to increase the risk of developing allergies. So there are two mechanisms at work -- on the one hand exposure to microorganisms has a protecting effect, but on the other allergens can elevate the risk. So there is only speculation at this point, not real proof. So I think there needs to be more work done on this subject."

More information

Learn about cutting down on pet and other indoor allergens from the American Academy of Allergy, Asthma and Immunology and the Nemours Foundation.

SOURCES: Eva Rönmark, Ph.D., Obstructive Lung Disease in Northern Sweden Study Group (OLIN), Department of Medicine, Central Hospital of Norrbotten, Lulea-Boden, Sweden; Marjan Kerkhof, Ph.D, medical researcher, University of Groningen, Netherlands; Journal of Allergy and Clinical Immunology

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