A clinical study of Japanese cedar (Cryptomeria japonica) pollen-induced asthma.

Background: Grass and birch pollens are known to induce asthma. However there are few reports about other pollen-induced asthma. Japanese cedar is the most common allergen in rhinitis in Japan but is controversial on whether it can provoke asthma.
Methods: To clarify Japanese cedar pollen-induced asthma, we studied adult patients who were sensitized only to the Japanese cedar (CAP-RAST > = 2) and had symptoms of asthma during the cedar season. We defined cedar asthma as a patient who satisfied the 2 criteria mentioned above.
Results: We found 6 adult asthma patients who fulfilled the two criteria. Five patients suffered from cedar pollinosis in addition to asthma, and 1 patient had no pollinosis. The cedar pollinosis preceded asthma in 3 cases and occurred at almost the same time in the other 2 cases. Pulmonary function was normal in these cases (FEV 1%, mean +/- SD, 76.5 +/- 10%), with a high threshold value in the non-specific airway hypersensitivity test (Ach-PC20, 2,696 to 20,000 microg/ml, 9294 +/- 2) and low total IgE (101 +/- 86 IU/ml). In the allergen provocation test, 3 subjects showed both an immediate and late asthmatic reaction.
Conclusions: We concluded that Japanese cedar pollen could provoke not only pollinosis but also asthma in adults.