Positive nasal challenge responses to Blomia tropicalis.

BACKGROUND: Blomia tropicalis, a dust mite commonly found in subtropical and tropical environments, is the fourth most common mite in the United States. Thirty-eight percent of 167 consecutive subjects evaluated for allergic respiratory symptoms in the Tampa Bay area had positive skin test responses to B. tropicalis.
METHODS: Nasal challenges were performed in 19 subjects with allergic rhinitis; 12 had positive skin test responses to B. tropicalis (group I), and seven had negative skin test responses to B. tropicalis but positive skin test responses to Dermatophagoides pteronyssinus and D. farinae (group II). Subjects were challenged with a normal saline control solution and increasing concentrations of a 1 mg/ml in-house extract of B. tropicalis (1:125,000 vol/vol, 1:25,000 vol/vol, 1:5000 vol/vol, 1:1000 vol/vol, and 1:200 vol/vol). Inspiratory nasal airway resistance (was measured every 5 minutes for 15 minutes by posterior rhinomanometry at 50 Pa after each nasal challenge.
RESULTS: Nasal challenge response was considered positive and stopped when the mean inspiratory nasal airway resistance was greater than twice the mean inspiratory nasal airway resistance after the normal saline challenge. Ten of 12 (83%) subjects in group I and none of seven (0%) subjects in group II had positive nasal challenge responses to B. tropicalis (p = 0.0024).
CONCLUSION: B. tropicalis is allergenic and should be considered as a cause of allergic rhinitis when evaluating a patient who lives in an area where it is endemic.