Orchid allergy.

A female office worker acquired contact allergy by handling Cymbidium cultivars for several years. The sensitizing properties of this ornamental orchid were demonstrated by experimental sensitization of guinea pigs. Chemical analysis of the ether extracts disclosed the presence of two quinones. The structure of the main quinone was elucidated as 2,6-dimethoxy-1,4-benzoquinone by x-ray crystallographic analysis. In the patient and in the sensitized animals, only this quinone elicited strong reactions, while tests with the second constituent were negative or gave only weak responses. Although 2,6-dimethoxy-1,4-benzoquinone is only a moderately strong sensitizer, its role as a contact allergen is emphasized, as it has been found in more than 50 different plant and wood species.