Celery is known to contain psoralens, a group of substances that cause
a toxic dermal reaction on exposure to ultraviolet A rays (UVA). An o
utbreak of phytophotodermatitis amongst 11 workers in a celery harvest
in southern Israel is reported. Methods. Analysis of the trigger fact
ors was carried out. The patients were questioned regarding their work
ing conditions. Samples of the celery that the workers had been harves
ting were analyzed for levels of total psoralens by means of high perf
ormance liquid chromatography (HPLC). Levels Of UVA were measured. Res
ults. It was found that the celery harvested in the south of the count
ry contained 84 mug/g fresh weight (f.wt.) total psoralens as compared
to 35 mug/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 co
ntained only 26 mug/g f.wt. total psoralens. Other risk factors noted
were that the subjects had fair skin, wore no protective clothing, and
worked with moist hands. In addition, the days were clear and sunny t
hus ensuring maximal uv radiation for that time of the year. Conclusio
ns. Multiple factors contributed to the outbreak of phytophotodermatit
is. 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.