[Allergy to cypress pollen: preparation of a reference and standardization extract in vivo].

Development of Cypress allergy frequency led to the standardization of commercial cypress extract used for diagnosis and immunotherapy. Previous in vitro studies on two cypress pollen species (Cupressus sempervirens and Cupressus arizonica) allowed us to produce an allergenic solution composed by a mixture of both extracts for in vivo standardization. Dilutions of this allergenic solution were tested by prick-test on 44 patients with clinical allergy to cypress pollen to define the dilution that corresponds to a 6 mm wheal conformed to the definition of 100 IR. The mixture of the two major species found in France is justified by the in vitro study results. Extracts revealed complementary allergenic composition: Cup sempervirens showed a wider diversity of allergens whereas Cup arizonica showed a higher content of the major 43 kDa allergen. Thus, according to in vivo analysis, we are able to produce a standardized extract of Cypress pollen expressed in IR.