AUGUSTA, Ga., Aug. 27 (UPI) -- Children in their first year of life who live with two or more cats or dogs have less chance of having common allergies later in life, a new study has found.
Kids raised with pets were only 31 percent as likely as children without pets to show common allergic responses by the time they were ages 6 to 7.
The exact mechanism accounting for this difference is not yet understood, however, according to lead researcher Dennis R. Ownby, professor of pediatrics and medicine at the Medical College of Georgia.
It is only hypothetical, Ownby said, but it may be that early exposure to certain types of bacteria residing in the digestive tract of cats and dogs -- such as Lactobacillus -- could affect development of a child's immune system. The part of the immune system regulating overall responses when it detects certain invaders in the body might learn to tone down its response if in frequent contact with pet-borne bugs, thereby reducing allergic reactions, he said.
"If additional research supports this work, then it's worth looking at the question on a molecular basis. Is there something in these bacteria that we could separate out and give to children ... in their first year of life that will produce this same effect?" Ownby said.
Although some recent research tends to support the new finding, the medical community long has believed exposure to that cats and dogs in the first year could lead to allergies.
The study, appearing in the Aug. 28 issue of the Journal of the American Medical Association, was completed by the Georgia scientists working with researchers in Detroit at the Henry Ford Health System and Wayne State University. In all, the team studied 474 children in suburban Detroit from birth through ages 6 to 7.
In the first year, investigators recorded the parents' allergic history, smoking habits and the numbers of siblings and pets. At age 2, allergens were collected from the homes and children tested for exposure to tobacco smoke. At ages 6 to 7 the children were tested for allergic reactions to cats, dogs, dust mites, ragweed and blue grass.
After statistical adjustments were made for parental asthma, allergies, smoking and the presence of siblings, the researchers concluded, "Exposure to two or more dogs or cats in the first year of life may reduce subsequent risk of allergic sensitization to multiple allergens during childhood."
If correct, the findings would fit with a controversial notion called the "hygiene theory" that states widespread protection against infection in modern cultures results in underdeveloped immune systems. For example, some studies have found prolonged exposure to farm animals also is correlated with fewer allergies.
Robert L. Roberts, associate professor of pediatrics at the David Geffen School of Medicine at the University of California at Los Angeles, who specializes in allergy immunology, told UPI, "The results are probably correct as far the numbers go." However, Roberts cautioned, "There is a danger, because we don't really know what the mechanism is, in telling parents '(to) avoid allergies, get two or more dogs or cats.' If a child is allergic to these, you'll have more trouble later."
Although acknowledging that the study appears solid and had adjusted for parental allergies, pediatric allergist Peyton Eggleston shared some of Roberts' concerns.
"We really need to see if these results can be repeated independently," Eggleston, a professor of pediatrics and head of the pediatric allergy program at Johns Hopkins Children's Center in Baltimore, told UPI. "As a practitioner, I have concerns about parents thinking that they should rush out and get a pet to protect their child. Ten (percent) or 15 percent of children in this study became allergic to the pet, and the family then faces the issue of removing the pet for their child's health."
Exposure to some bacteria in the gut of cats and dogs might reduce allergies, according to Pedro Avila, an assistant clinical professor of medicine and pediatrics at the University of California at San Francisco. "There are even trials now of giving Lactobacillus to pregnant women and to newborns in the first month of life. Preliminary results show that may decrease the incidence of allergies," Avila, who specializes in allergies and immunology, told UPI.
(Reported by Joe Grossman, UPI Science News, in Santa Cruz, Calif.)
