Phototoxicity from furocoumarins (psoralens) of Heracleum laciniatum in a patient with vitiligo. Action spectrum studies on bergapten, pimpinellin, angelicin and sphondin.

Investigations on light reactions in a patient with vitiligo are presented. The minimal erythema dose (MED) in the UVB area was approximately 1/3 of that in persons of skin type II. The application of furocoumarins (psoralens) increased light tolerance by 1 MED at 300-310 nm. Action spectrum studies with furocoumarins from Heracleum laciniatum showed the following order of potency: bergapten, pimpinellin, angelicin and sphondin. The efficacy was highest at 325-350 nm, with maxima at 330-335 nm. Pimpinellin was recently found to be phototoxic, but an action spectrum of sphondin is reported for the first time.