June 13, 2011— -- Childhood pets don't necessarily lead to allergies later in life, new study findings suggest.
Researchers from Henry Ford Hospital in Detroit assessed more than 550 18-year-olds who were enrolled at birth in the Detroit Childhood Allergy Study from 1987 to 1989. They found that children who had a dog or a cat were not at increased risk for developing future pet allergies.
Indeed, the study found that boys who had dogs and teens who had cats during their first year of life had 50 percent less risk of developing pet allergies later.
"The first year of life is the critical period during childhood when indoor exposure to dogs or cats influences sensitization to these animals," the authors theorized in the study.
The exact reasons for such early sensitization are still unknown but, the researchers and other allergists say, there is a popular theory behind it.
The results suggest that the "hygiene hypothesis" is valid, meaning that exposure to certain environmental factors, such as animals or dust, might trigger an infant's immune system to develop tolerance for allergens and the end result is that the child has reduced likelihood of developing allergic disease," said Dr. Stanley Fineman, president-elect of the American College of Allergy, Asthma and Immunology. Fineman was not involved with the pet allergy study.
Allergists also say the study only looks at the development of antibodies to dog and cat allergens, not full-blown allergies.
"While allergic antibody is a risk factor for developing clinical allergy to that exposure, less than half of all presence of allergic antibody is associated with clinical allergy," said Dr. Miles Weinberger, professor of pediatrics at the University of Iowa Children's Hospital In Iowa City.
'Hygiene Hypothesis' Still Unproven
Genetics, he said, might play a bigger role than simply having a pet.
"The predisposition to develop allergic antibody is genetically determined," he said. "It is, therefore, quite likely that the presence or absence of cats or dogs in the house relates to clinical sensitivity of parents or other family members."
While the study does offer some support for the hypothesis that having pets doesn't make children more allergic to them in the future, this theory still needs to be proven, experts say.
"I would not recommend that parents rush out to get a pet for their infant in the hopes of reducing the likelihood that their child will develop allergic disease," Fineman said.