Prevalence of house dust mites in the Rocky Mountain states.

BACKGROUND

Due to low rainfall and high elevation the ten Rocky Mountain states would not be expected to have the indoor humidity required to support the growth of significant numbers of house dust mites. Nevertheless, a recent survey reported that house dust mite allergen levels were not significantly different in the various regions of the United States, including the arid and mountainous regions.

METHODS

Each summer for 5 years (1988-92) patients with bronchial asthma scheduled to be evaluated at the National Jewish Center for Immunology and Respiratory Medicine were invited to submit a dust sample from their mattress or bedroom carpet for mite analysis.

RESULTS

Fifty-eight patients from the ten Rocky Mountain states submitted dust specimens. Forty-eight contained no mites, five had levels of mites considered clinically insignificant (less than 100 mites/g dust), three contained 100 mites/g of dust, a level at the threshold of significance, and two had high levels of mites (1,000 and 3,000 mites/g). Both of the homes with high mite levels had specific sources of excess moisture. Twenty-eight patients from adjacent states also submitted dust specimens. Significant levels of mites were encountered in specimens from these states reflecting the transition to zones of greater humidity and lower elevation.

CONCLUSION

Except in homes with unusual sources of humidity, significant levels of house dust mites are rarely encountered in homes in the ten Rocky Mountain states.