"We simply started looking at our data to see if exposure to dogs and cats really increases the risk and the data didn't look the way it was supposed to; as a matter of fact, it was very strongly the opposite of what we expected to find," said Dr. Dennis R. Ownby, chief of the Medical College of Georgia Section of Allergy and Immunology and lead investigator on the study published in the Aug. 28 issue of the Journal of the American Medical Association.
"Allergists have been trained for generations that dogs and cats in the house were bad because they increased the risk of you becoming allergic to them; we know that before you become allergic to something, you have to be repeatedly exposed to it."
But when doctors followed a group of 474 healthy babies in the Detroit area from birth to about age 7, comparing the 184 exposed during infancy to two or more dogs or cats to the 220 who were not exposed to these animals, they found that the children exposed to two or more indoor pets were half as likely to develop common allergies.
Also, fewer of the children who had early exposure to indoor pets had hyper-responsive and easily irritated airways, a risk factor for asthma. Reactivity was based on the airway's response to a chemical stimulant called methacholine. In fact, children raised with two or more dogs or cats had 45 percent less hyper-reactivity; rates went from 24.1 percent to 15.8 percent. The boys experienced an even greater reduction, from 25.5 percent for boys with no indoor pets to 5.1 percent for those with multiple pets. About 7 percent of the children developed asthma during the study, which is on target for national averages.