Control of house dust mites by electrical heating blankets.

The contents of house dust mites, Dermatophagoides (D), in 10 beds supplied with electrical heating blankets (EHBs) and in 10 control beds were followed for 1 year. All beds were in regular use during the study period. Dust from mattresses and EHBs was collected monthly and analyzed for D by microscopy. Blankets were turned on during daytime and were washed every 3 months. For each bed the median concentration of D during the entire period was related to initial value. In the beds supplied with blankets, the overall median was 52% compared to 122% in the control beds (p less than 0.05). The difference between the two groups of beds was observed within the first month. Major antigens from D were reduced to 32% in the beds supplied with blankets and increased to 120% in the control beds (p less than 0.05). Climatic conditions were measured beneath the blanket in a spare bed. When beds were covered by eiderdown, temperature was increased by 26 degrees C, and the relative humidity was decreased by 24% within 3 hours. In conclusion, EHBs appear capable of reducing relative humidity and concentration of house dust mites on mattress surfaces.