Kids who spend less time during their early years around pets and dust don’t appear to have a lower risk of developing asthma or respiratory problems, new research reports.

These findings contradict a long-held theory that protecting children from substances that can trigger allergies or asthma - known as allergens - may protect them from respiratory problems later in life.

Study author Dr. Paul Cullinan of the National Heart and Lung Institute in London explained that, consequently, parents who want to protect their children from developing allergies or asthma “should not worry too much about allergen levels in their home.”

The reason the researcher and his colleagues may have failed to find an effect of early exposures on allergy risk could be because the relationship between the two is not “straightforward,” Cullinan said.

For the study, the team followed 625 children from birth, and tested the levels of the dust mites - the tiny critters that dwell in house dust and are a common trigger of allergic reactions - and cat dander in their living rooms when they were only 8 weeks old.

The researchers then interviewed mothers once per year and asked if their children had had any trouble breathing during the past year, and tested children at age 5-1/2 to determine if they had any sensitivity to dust mites or cat dander. An individual’s sensitivity is gauged using a skin prick test with the specific allergen and noting any reaction.

Reporting in the journal Thorax, the investigators found that one in 10 children were sensitive to dust mites or cat fur, and one in 14 had experienced wheezing.

The researchers found that the risk of becoming allergic or asthmatic increased with exposure to very low levels of allergens during their first years of life. That risk flattened out with higher exposures, the authors note.

The increase in risk with little allergen exposure was primarily seen in first-born children and those with a family history of allergies.

These findings “make it improbable that reductions in domestic allergen exposures alone will have a major impact in reducing the incidence of these diseases in childhood,” the Cullinan’s team writes.

In an accompanying editorial, Dr. A Custovic of Wythenshawe Hospital in Manchester, UK and colleague say that the body of evidence surrounding early exposures and allergy risks “appears inconsistent and often confusing.”

Collectively, these studies demonstrate that one single recommendation - such as, shield your children from allergens - will likely not succeed on a wide scale, they note.

“We need to move away from the concept of blanket advice aimed at the whole population to tailor-made individualized measures targeting individuals with specific susceptibilities who will benefit from a particular intervention,” they note.

SOURCE: Thorax, October 2004.