Bald cypress tree (Taxodium distichum) pollen, an allergen.

Fifty-seven nasal and bronchial provocation tests were performed with bald cypress pollen extract (BCE) on 41 subjects. A positive nasal response was elicited in 12 of 17 (71%) subjects with allergic rhinitis and positive BCE skin tests, and in none of 16 control subjects. A positive bronchial challenge was elicited in two of ten extrinsic asthmatics with positive BCE skin tests, and in none of 14 control subjects. BCE-specific IgE was demonstrated by RAST in seven of the 12 (59%) subjects with a positive nasal challenge and in one of the two with a positive bronchial challenge. BC pollen is an aeroallergen.