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Am Fam Physician. 2017;96(10):online

Clinical Question

Can mite-impermeable bedding decrease asthma exacerbations in children with asthma who are sensitive to mites?

Bottom Line

In children with house dust mite allergies and asthma, the use of mite-impermeable bedding decreases the frequency of asthma exacerbations. (Level of Evidence = 1b–)


House dust mites are a common allergen associated with asthma. This U.K. study included children with physician-diagnosed asthma who visited the hospital for an exacerbation (emergency department or admission). After the exacerbation had cleared, the researchers skin tested the children for house dust mite, cat, dog, pollen, and other allergens. They randomized children who had a wheal at least 3 mm larger than the negative control to receive mite-impermeable bedding covers (n = 146) or identical but nonimpermeable bedding covers (n = 138) to use at home. The researchers gave all participants the same instructions on the care of the bedding covers, and none were given instructions on mite avoidance. In the event that a second child from the same family entered the study, the researchers assigned them to the same intervention. Interviewers unaware of group assignment interviewed the child's primary caregiver one, four, eight, and 12 months after enrollment to ascertain exacerbations, unscheduled medical care, medication use, and quality of life. Additionally, the researchers vacuumed the child's bedroom floor at baseline and at the end of the study to estimate the mite load in the room.

At the end of one year, 23 children in the mite-impermeable bedding group dropped out compared with 20 in the control group. Although this 15% dropout rate is not a major problem, it is still a bit worrisome. At the end of one year, 29% of children in the mite-impermeable bedding group had exacerbations leading to a hospital visit compared with 42% of the control group (number needed to treat = 9; 95% confidence interval, 5 to 512). However, approximately one-half of the children in each group used oral corticosteroids during the year. Approximately 25% of the children reported that the special bedding covers were uncomfortable and thought about removing them, as did less than 3% of the children with the regular covers. These mite-impermeable bedding covers cost approximately $200 in the United States.

Study design: Randomized controlled trial (double-blinded)

Funding source: Foundation

Allocation: Concealed

Setting: Inpatient (any location) with outpatient follow-up

Reference:MurrayCSFodenPSumnerHShepleyECustovicASimpsonAPreventing severe asthma exacerbations in children. A randomized trial of mite-impermeable bedcovers. Am J Respir Crit Care Med2017;196(2):150–158.

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