[Plasma levels of psoralens after celery ingestion]

Psoralens are photosensitizing substances present in many vegetables, some of which are routinely consumed. These vegetables are responsible for contact phytophotodermatitis, but it was agreed that they did not produce photodermatitis when taken orally. Ljunggren has recently questioned this concept by reporting a case of phototoxic accident which occurred after ingestion of 450 grams of celery roots (Apium graveolens). In a study in healthy volunteers we looked for psoralens in blood and analyzed the cutaneous photosensitivity by the minimal phototoxic doses (MPD) method, after ingestion of celery in large amounts (500 grams and more). Plasma concentrations of psoralens were inexistant in all subjects and at all sampling times, and no phototoxic reaction was detected by MPD. Celery roots, therefore, do not seem to be photosensitizing, even after ingestion in large amounts, but they might increase the risk of phototoxicity in PUVA-therapy. The same applies to fennel and parsnip.