Background: Although allergy to Cannabis sativa was first reported over 40 years ago, the allergenicity has scarcely been studied. The objectives of this study were to investigate the frequency of sensitization to this plant, to analyze the clinical characteristics and allergenic profile of sensitized individuals and to identify the allergens involved. Methods: Five hundred and forty-five individuals in Spain attending allergy clinics with respiratory or cutaneous symptoms underwent a skin-prick test (SPT) with C. sativa leaf extract. The extract was characterized by SDS-PAGE and 2-dimensional electrophoresis. Specific IgE to C. sativa was measured in positive SPT individuals. The clinical and allergenic profiles of sensitized individuals were investigated and the most-recognized allergens sequenced and characterized by liquid chromatography-mass spectrometry/mass spectrometry. Results: Of this preselected population, 44 individuals had positive SPT to C. sativa (prevalence 8.1%). Prevalence was higher in individuals who were C. sativa smokers (14.6%). Two individuals reported mild symptoms with C. sativa. Twenty-one individuals from 32 available sera (65.6%) had positive specific IgE to C. sativa. Twelve sera recognized at least 6 different bands in a molecular-weight range of between 10 and 60 kDa. Six of them recognized a 10-kDa band, identified as a lipid transfer protein (LTP) and 8 recognized a 38-kDa band, identified as a thaumatin-like protein. Conclusions: There is a high prevalence of sensitization to C. sativa leaves. The clinical symptoms directly attributed to C. sativa were uncommon and mild. The sensitization profile observed suggests that C. sativa sensitization may be mediated by two mechanisms, i.e. cross-reactivity, mainly with LTP and thaumatin-like protein, and exposure-related ‘de novo' sensitization.

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Background: Cases of allergy to Cannabis sativa have occasionally been reported, but both the allergenic profile and eventual cross-reactivity pattern remain unknown. Objective: To analyze the allergenic profile of a population of patients from Spain sensitized to C. sativa and to characterize the C. sativa leaf extract. Methods: A total of 32 subjects were enrolled in the study: group A, 10 individuals sensitized to tomato, reporting reactions by contact or inhalation to Cannabis; group B, 14 individuals sensitized to tomato, without reactions to Cannabis; group C, 8 individuals not sensitized to tomato and without reactions to Cannabis. Sensitivity to Cannabis, tomato and peach peel, Platanus hybrida and Artemisia vulgaris pollen extracts was measured by skin tests and specific IgE. Individual immunoblots and inhibition experiments with a pool of sera were conducted. Results: All tomato-sensitized subjects (and 1 negative) had positive skin tests to C. sativa leaves and hashish. Specific IgE to C. sativa and peach peel was more common than to tomato. Immunoblot experiments showed 2 prominent bands of 10 and 14 kDa and 2 weakly recognized bands of 30 and 45 kDa. Tomato, peach and A. vulgaris extracts inhibited most of the bands present in C. sativa. P. hybrida inhibited only the high-molecular-weight bands. Conclusion: Sensitization to C. sativa with or without symptoms is frequent among patients in Spain sensitized to tomato. C. sativa leaves are a potential allergenic source and their allergens may cross-react with other allergenic sources from plants (fruit peels and pollen).

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The prevalence found of skin test sensitivity to tomato is high. Peel extracts detected most of the sensitized subjects. Most of the sensitized subjects were asymptomatic and some patients reported symptoms without skin test sensitivity. Positive subjects were very frequently sensitized to pollens, suggesting allergen cross-reactivity. Regional differences may exist, possibly related to the pattern of sensitization to cross-reacting pollens.