Pet Risk To Allergies, Asthma Unclear

May 31 -- If you worry that your Siamese will give your kid the sniffles or your Newfoundland will make your namesake wheeze, don't shuffle your pets off to the pound quite yet.

That's because while there is an abundance of evidence suggesting relationships between the presence of pets in the home and allergies and asthma, there is no clear consensus on what it all really means.

For example, a recent study published in the May issue of the Journal of Allergy and Clinical Immunology found that among Finnish adults, the risk of developing asthma was higher amongst those who had previously owned pets.

But there are also studies suggesting that living with pets can actually protect the children who are raised with them from allergies and asthma.

"It's certainly too early to make a firm statement as to what parents should do," says Dr. Thomas Platts-Mills, chief of the division of allergy and professor of medicine and microbiology at the University of Virginia.

'The Thanksgiving Effect'

It appears that several factors come into play — and researchers are not yet clear which ones are be the most important.

"One of the leading hypotheses is that the timing of the exposure [to pets] is critical," says Dr. Bruce Lanphear, associate professor of pediatrics and director of the Environmental Health Center at Cincinnati Children's Hospital Medical Center. "It may be that if you are exposed early in life you are protected, or it may be that if you are exposed early you are at increased risk."

Research findings have supported both ideas. A study published in The Lancet in March 2001 suggested that children growing up in houses with cats produced antibodies to cats (a hallmark of an allergic response), but did not show increased risk of allergies or asthma.

"We're pretty sure that the cat can induce a form of tolerance," says Platts-Mills who conducted the research.

Another observed effect of exposure to allergens like pets suggests that this tolerance may not always last one's entire life. Children who spend the first 17 years of life living with a cat and then spend some time away — in college for example — will often have more severe allergic reactions to the cat upon returning home. Allergists dub this "The Thanksgiving Effect."