Therapeutic and Drug Brief
House Dust Mites and Asthma
Over the last 20 years, the prevalence of asthma has increased. For instance, in Australian children ages 8-11, wheezing and bronchial hyperresponsiveness prevalence have doubled. Asthma has been associated with sensitization to house dust mites (HDM). The greatest reservoir of HDM is in carpets and mattresses. Improvements in symptoms, histamine-induced bronchial hyperactivity, and sensitivity to HDM challenge have been demonstrated when sensitive individuals are moved to antigen-free environs.
A study by Hill and colleagues examined over a five-month period the HDM antigen in the home situations of 88 children with proven HDM sensitivity.1 Comparisons were made between carpeted and uncarpeted bedrooms, between various types of mattress covers, and other carpeted vs. non-carpeted areas of the homes.
Mattresses that were encased in impermeable covers had a 20-fold lower concentration of HDM antigen than typical cotton, wool, or sheepskin covers. This absolute concentration is considered to be below the necessary threshold to induce HDM sensitivity. Concentrations of HDM antigen in house dust were at least five times greater in carpeted than non-carpeted rooms.
Hill et al conclude that excluding home carpeting and using impermeable mattress covers reduced absolute HDM antigen levels. This type of intervention could have long-term implication in development of asthma and atopic disease on a public health basis. Although powdered agents (acaracides) reduce HDM infestation and antigen, they are costly, require substantial effort to use, and are less effective than these much simpler measures.