Phytophotodermatitis: an experimental study using the chamber method.

Experimental phytophotodermatitis was produced using crushed leaves from the gas plant, Dictamnus albus. The tests were made using the chamber method and irradiated with ordinary black light tubes. An occlusion time of not less than 30 min was needed to give a phototoxic reaction in all test subjects. An occlusion time 30-120 min gave the optimal results, but contact for 24 h produced only weak and inconsistent reactions. The phototoxic substance was readily absorbed into the skin within 10-15 min. The phototoxic tendency already began to disappear within 30 min after the tests were removed. UVA energy of 0.3 J/cm2 was enough to evoke a phytophotoreaction in all of the test subjects when other conditions were optimal. The reactions were enhanced by adding water to the test sites. Deep-freezing of the plant material did not destroy the phototoxicity within a 4-month period.