The effects of season, climate, and air-conditioning on the prevalence of Dermatophagoides mite allergens in household dust.

BACKGROUND: Clinical evidence reveals a strong relationship between dust mite allergen levels and asthma. This study suggests the relative importance and interactions among factors that influence mite allergen levels in human dwellings.

METHODS: Dermatophagoides pteronyssinus allergen (Der p I) and D. farinae allergen (Der f I) were measured in 536 dust samples collected from 424 homes across the United States.

RESULTS: There were distinct seasonal fluctuations of Der p I and Der f I. Der p I rapidly increased to peak in July then gradually decreased through October. Der f I slowly rose to peak later, around September, before declining. Different climates in regions of the United States had no significant affect on the quantity of Der p I or Der f I. However, regional climate differences seemed to influence the prevalence of either D. pteronyssinus or D. farinae. Air-conditioning significantly reduced (p < 0.001) Der I mite allergens detected in the dust samples, and a tendency existed for Der f I to be higher than Der p I in air-conditioned homes. There was a significant (p < 0.01) interaction between air-conditioning and seasons. The most dramatic affect was observed during the summer months, the cooling season, from approximately May to September.

CONCLUSIONS: These findings show that distinct seasonal fluctuations exist of D. pteronyssinus and D. farinae mite populations, and suggest that differences in the microclimate within homes may have a dramatic affect on Dermatophagoides mite populations.