The natural history of mountain cedar pollinosis.

During the winter months, pollen from the mountain cedar (MC) (Juniperus sabinoides) causes severe respiratory tract allergy in central Texas. We have been impressed with the fact that many of our MC-allergic patients had only allergic rhinitis and were only sensitive to MC pollen. We therefore studied 234 unselected MC-allergic patients at the end of the MC season. The main criteria for inclusion into the study was a bona fide history of MC pollinosis confirmed by a positive skin test. All patients completed a detailed history questionnaire, were prick skin tested by using 1:20 w/v, extracts, and had a total IgE determined with commercially available reagents (PRIST). Thirty-four percent of patients were found to be allergic only to MC and 66% were allergic to MC and other aeroallergens. As a group, patients allergic only to MC had significantly lower total IgE levels (84 IU/ml vs. 360, p < 0.001) (normal < 180), required much longer exposure intervals to cedar pollen before developing MC pollinosis (14.4 yr vs, 5.69, p < 0.001), had less of a family history of allergic disease (43% vs. 88%, p < 0.001), had less of a history of asthma or eczema (11% vs. 39%, p < 0.001), and developed allergic disease at a later age (39 yr vs. 13, p < 0.001) when compared to patients with multiple allergies. These results suggest that the MC pollen may be unique in causing allergic rhinitis in patients who have no other sensitivities. A possible explanation may lie in the carbohydrate nature of the main allergen of the MC pollen, which may facilitate allergen transport through the respiratory tract mucosa and subsequent sensitization.