Tackling Several Allergens at Once to Prevent Asthma in Kids

Reducing children’s exposure to a variety of allergens, rather than targeting a single “trigger,” might be a better way to avoid asthma, according to a new review of studies.

While some children are genetically predisposed to developing the disease, parents might still be able to prevent or delay the onset of symptoms by minimizing exposure to likely allergens.

“Breastfeeding and house dust mite reduction seemed to be the most important interventions,” used in the studies, said review author Tanja Maas. “The food interventions focused on hydrolyzed formula as opposed to regular formula. The use of hydrolyzed formula was not shown to have any preventive effect. Breastfeeding, however, seemed to be very effective.”

Reviewed studies focused on 3,271 high-risk children — those having at least one close relative with asthma.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.

Led by Maas, a researcher of immunological disease at Maastricht University Medical Center, in the Netherlands, the authors analyzed nine studies. They classified three of the studies as multifaceted, taking more than one approach to asthma prevention. These studies covered both inhalant and dietary types of allergen reduction, while the remaining six studies looked at one type of allergen reduction alone.

Dietary restrictions started in pregnancy or from the child’s birth. In studies that included a dietary approach, mothers were encouraged to breastfeed or use special formula and to delay the introduction of solid foods into the child’s diet. Environmental interventions included the reduction of dust mites, pet allergens and exposure to tobacco smoke in the child’s immediate environment.

The majority of allergic sensitization probably happens in early childhood or adolescence.

“We see most seasonal allergy sensitization occur by five years of age,” said pediatric allergist Harvey Leo, M.D., an assistant research scientist at the Center for Managing Chronic Disease at the University of Michigan. “Eighty percent of food allergies are present by two to three years of age.”

Complicating study results was the fact that physicians cannot make a definitive diagnosis of asthma in children younger than five years, although the studies did include children whose parents had reported asthma-like symptoms such as wheezing and nighttime coughing.

“Children under the age of five are too young to diagnose with asthma, as the instructions used in determining lung-function measurements are too difficult for a child to comprehend, but asthma-like symptoms give some information on the respiratory health of the child,” Maas said.