The use of domestic steam cleaning for the control of house dust mites.

BACKGROUND Control of dust mites using extremes of temperature is an alternative to the use of acaricides. In the past we have attempted control by freezing with liquid nitrogen. The present paper deals with the opposite extreme, the use of steam. OBJECTIVE To assess the feasibility and effectiveness of a domestic steam cleaner for the control of dust mites, its effect on mite populations and concentrations of the allergen Der p 1. METHODS A domestic steam cleaner was used to treat carpet squares that had been seeded in the laboratory with known numbers of dust mites (Dermatophagoides pteronyssinus). The number of live mites was monitored for a period of 4 months in eight treated carpet squares and eight controls. Dust samples were taken from 12 standardized areas of carpet in a tenement flat in Glasgow, UK, before and after steam cleaning treatment, and the concentration of allergen Der p 1 was compared with 12 adjacent, control areas. RESULTS No live mites were found at any time in the treated carpet squares, whereas in the control squares geometric mean mite population density rose from 11 after 3 days to 39 after 1 month, 66 after 2, 122 after 3 and 185 after 4 months. There was a mean reduction of 86.7% in Der p 1 concentration (3.3-0.44 microgram/g) compared with a reduction of 4.7% (2.22-2.116 micrograms/g) in control areas, a difference that was statistically significant at the 5% level. CONCLUSION These data indicate that steam cleaning has considerable potential as an highly effective and efficient method of killing dust mites and reducing concentrations of Der p 1 in domestic premises.