Allergen reduction with mite-impermeable mattresses ‘of no asthma benefit’
MedWire News: Mite-impermeable mattresses reduce exposure to house dust mite (HDM) allergen Der f1 but have only a temporary effect on childhood asthma symptoms and no effect on the risk for allergy-associated conditions, European results indicate.
Previous studies have demonstrated that exposure to high levels of HDM allergens early in life is linked to the developments of allergic sensitization, and interventions to control HDM levels are associated with reductions in HDM allergen levels. However, neither exposure to allergens nor interventions to reduce exposure have been consistently linked to the development of asthma and allergies.
To determine the impact of an early intervention with a mite-impermeable mattress on HDM allergen levels, and subsequent asthma and allergy, Ulrike Gehring, from Utrecht University, in the Netherlands, and colleagues randomly allocated 416 high-risk children with allergic mothers to use mite allergen-impermeable mattress covers, a further 394 high-risk children to use placebo mattress covers, and 472 children to use no intervention.
Questionnaires on asthma and allergy were administered yearly, and specific immunoglobulin E and bronchial hyperresponsiveness were determined at 8 years of age. In addition, mattress dust samples collected at different time-points were assessed for HDM allergens.
The results, published in Allergy, show that compliance was slightly higher with active covers versus placebo covers, and significantly higher in families with fathers allergic to HDM than in those without.
Although there were no differences in allergen levels between active and placebo groups on intention-to-treat analysis at 8 years, adherent-to-protocol analysis indicated that levels of Der f1, but not Der p1, allergen levels were significantly reduced in the active group. There were no differences between the placebo and no intervention groups.
There was a temporary decrease in asthma symptoms at 2 years of age in the intervention versus placebo group, but no decrease in the risk for asthma and allergies at 8 years with active intervention.
While there was an increased risk for asthma among children with the highest total HDM exposure, there was no dose-response relationship and no link between levels of individual allergens and health outcomes.
The researchers write: "Up to now, significant reductions in asthma, allergies, and related symptoms have only been reported in studies where HDM allergen interventions were part of a multifaceted intervention program including additional intervention measures such as avoidance of food and pet allergens or passive smoking. Together, this suggests that interventions with reduction in HDM allergen exposure only are probably insufficient."
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By Liam Davenport