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.