Tuesday, July 25, 2006 (Reuters Health)—House dust mite allergen (HDM) avoidance and dietary fatty acid modification in the first few years of life do not prevent asthma, eczema, or atopy in children with a family history of asthma, new research shows.

Sensitization to HDM and consumption of diets with a low omega-3 to -6 fatty acid ratio have been linked to asthma. In the present randomized trial, Dr. Guy B. Marks and colleagues assessed whether modification of these factors could actually prevent asthma and allergic disease in young children.

The study, which is reported in the July issue of the Journal of Allergy and Clinical Immunology, involved 616 children who were randomized to receive HDM avoidance, a diet with an increased omega-3 to -6 fatty acid ratio, both interventions, or no intervention during the first 5 years of life. Of these children, 516 were available for evaluation at 5 years.

The HDM avoidance measure involved the use of allergen-impermeable linens and regular washing with an anti-HDM detergent. With the diet intervention, parents were encouraged to prepare their child’s meals using canola-based oils and tuna oil capsules to achieve a high omega-3 to -6 fatty acid ratio.

Although HDM avoidance measure reduced bedding allergen levels by 61%, it had no effect on the occurrence of asthma, wheeze, or atopy, Dr. Marks, from the Woolcock Institute of Medical Research in New South Wales, Australia, and colleagues note. In fact, eczema was actually more common in the HDM avoidance group than in controls: 26% vs. 19%.

Similarly, while the diet intervention did succeed in increasing the omega-3 to -6 fatty acid ratio, it did not prevent asthma, wheezing, eczema, or atopy, the results indicate.

Despite the null findings of the present study, previous reports “support the view that, under certain circumstances, asthma can be prevented,” the authors state. “However, the most effective, practical forms of early life environmental modification and the circumstances under which it will be appropriate to implement them remain to be established.”