Background. Celery is known to contain psoralens, a group of substances that cause a toxic dermal reaction on exposure to ultraviolet A rays (uva). An outbreak of phytophotodermatitis amongst 11 workers in a celery harvest in southern Israel is reported.
Methods. Analysis of the trigger factors was carried out. The patients were questioned regarding their working conditions. Samples of the celery that the workers had been harvesting were analyzed for levels of total psoralens by means of high performance liquid chromatography (hplc). Levels of uva were measured.
Results. It was found that the celery harvested in the south of the country contained 84 μg/g fresh weight (f.wt.) total psoralens as compared to 35 μg/g f.wt. in celery harvested in the north of the country at the same time. The following year the celery harvested in the south contained only 26 μg/g f.wt. total psoralens.
Conclusions. Multiple factors contributed to the outbreak of phytophotodermatitis. A late harvest in the south of the country is incriminated as the cause of the unusually high levels of psoralens in the celery of that year.