Cypress Pollinosis: from Tree to Clinic

Cypress (Cupressus sp.pl) is a genus within the Cupressaceae family. This family covers all of the Earth's continents except for Antarctica, and it includes about 160 species. The most important taxa for allergic diseases belong to five different genera: Cupressus, Hesperocyparis, Juniperus, Cryptomeria, and Chamaecyparis. Cupressaceae species share a common pollen type that can even include the genus Taxus (Taxaceae) when this plant is also present. As Juniperus oxycedrus pollinates in October, Cupressus sempervirens in January and February, Hesperocyparis arizonica (prev. Cupressus arizonica) in February and March, and Juniperus communis in April, the symptomatic period is long-lasting. Due to global warming, the pollination period tends to last longer, and there is a trend for Cupressaceae bioclimate niches to migrate north. In Mediterranean areas, C. sempervirens (Italian cypress or Mediterranean cypress) is by far the most common pollinating species. It accounts for half of the total pollination level. The group 1 major allergens belong to the pectate-lyase family, and members share 70 to 97% sequence homology within the different Cupressaceae. Group 2 allergens correspond to the polygalacturonase protein family, while group 3, a minor allergen, belongs to the family of "thaumatin-like proteins," a pathogenesis-related protein 5. Group 4 allergens are Ca⁺⁺-binding protein (4 EF-hands). Aside from these four groups, about 15 other allergens have been reported. Prominent among these is a basic low-molecular mass cross-reactive allergen that was identified recently, and which is suspected to be involved in pollen food syndromes which are common with peach and citrus. The prevalence of cypress allergy in the general population ranges from 0.6 to 3%, depending on the degree of exposure to the pollen. Depending on the geographic area and the studied population, 9 to 65% of outpatients consulting an allergist may have sensitization to cypress pollen. Repeated cross-sectional studies performed at different time intervals have demonstrated a threefold increase in the percentage of cypress allergy around the Mediterranean area. Risk factors include a genetic predisposition and/or a strong exposure to pollen, and the natural history of cypress allergy allows identification of a subgroup of patients as allergic rather than atopic. Concerning the clinical expression, rhinitis is the most prevalent symptom, while conjunctivitis is the most disabling. Pharmacological treatment of cypress allergies is not different from that of other seasonal allergies. Immunotherapy has been used, initially by subcutaneous injections, but currently mostly through the sublingual route. Although clinical trials have included only a limited number of patients, it has proven effective and safe. Avoidance can be implemented at the individual level, as well as at the community level, through the use of alternative plants, low-pollinating cypresses, or by trimming hedges before pollination.