BOSTON, Sept. 5 (UPI) -- Researchers at the Channing Laboratory at Brigham and Women's Hospital said Thursday that asthma may be an exception to the new idea among some allergists that many children will show reduced allergic responses as adults if exposed to cats or dogs as infants.
Children who have a mother with a history of asthma will not get the same protective effect against allergies by having a cat in the house as a child whose mother does not have asthma, the researchers claimed.
A history of asthma in a child's father, however, does not increase risk for children who had cats, concludes the new study, published in the Sept. 7 issue of The Lancet.
For years, allergists believed that exposure to cats and dogs could lead to allergies. But now, the thinking is that having at least two pets -- dogs or cats -- in the home may benefit infants with developing immune systems.
Some studies have shown that children exposed to cats, dogs or farm animals have fewer allergies later in life.
The Channing study confirms the revised view, but it also says the situation for a child with a cat and an asthmatic mother is the exception to the "pets confer protection" idea.
Lead author Juan C. Celedón told United Press International: "The basic message is that, for most children, exposure to a cat in early life may be beneficial, but that there is a subgroup of children, those whose mothers have asthma, and perhaps those whose mothers are allergic to a cat, in whom exposure to a cat early in life may be detrimental."
The researchers studied 448 children who had at least one parent with atopy, an inherited tendency to allergic responses. The researchers gathered data by questionnaire and by testing for cat allergens in the home when the children were 2 months old.
The study used wheezing as an indicator of an allergic response. In asthma, the air passageways in the lung become narrow. Wheezing, which by itself is not diagnostic for asthma, often is a symptom of this narrowing. Many children at risk for atopy who are wheezing at age 5 are likely to develop asthma.
Children who were exposed to cats at 2 months of age and whose mothers had a history of asthma were about 3 times as likely to be wheezing by age 5 as children with asthmatic mothers who did not have cats. In contrast, children whose mothers were not asthmatic showed reduced wheezing by age 5 if they had a cat in the home at age 2 months.
The researchers said their conclusions only can be generalized to children of people with an inherited tendency to allergic response.
Andrew Liu, associate professor of pediatric allergy at National Jewish Medical and Research Center in Denver, told UPI: "If this is true, then it will be quite interesting to determine what contributes to benefit or harm from early life cat exposure. For example, is there an inherited airways vulnerability to cat exposure that can be passed from asthmatic mothers to their children?"
The overall picture still is not definitive. Philip E. Gallagher, a member of the public education committee of the American Academy of Allergy, Asthma and Immunology, and a practicing allergist in Erie, Pa., told UPI: "It's a hot topic of research over the past few years and depending on how you look at it, you can come up with different answers.
"It's difficult to compare study populations ... There are confounding factors in many of these studies that make the picture not completely clear."
(Reported by Joe Grossman, UPI Science News, Santa Cruz, Calif.)
