Background: Respiratory allergy to the pollen of Cupressaceae is becoming more and more common every year in the Mediterranean area.

Objective: The purpose of this study was to see whether the allergenic potency of Cupressus arizonica pollen diminished after a 6-year period (1994-2000).

Materials and Methods: Among the Cupressaceae, we selected the pollen of C arizonica. The mode of sampling in 1994 and in 2000 was the same and the pollen was collected on the same tree and stored at room temperature. To compare its biological and allergenic activities data was collected with the following methods: cytohistology of
Alexander, 2,3,5-triphenyltetrazolium chloride enzyme staining, skin testing, nasal provocation test, radioallergosorbent test (RAST), RAST inhibition, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and immunoblotting to detect protein content. Thirty-eight patients with respiratory allergy to Cupressaceae were selected.

Results: We found no decrease in the allergenic potency of the pollen, but did find that viability and germinating power had disappeared completely after 30 to 40 days. Moreover, the amount of protein in the old pollen was half the amount found in the fresh one. Skin prick testing showed identical results with the old and the fresh pollens.

Conclusions: The allergenic in vivo and in vitro activity of cypress pollen is retained for years after its collection. This activity seems to be independent of the viability of pollen grains and of the total protein content. This may
explain the presence of clinical symptoms in patients out of the pollen season.

Key words: Cupressus arizonica. Allergenicity. Pollen viability