Lichen planus in relation to occupational and non-occupational exposure to chemicals.

Lichen planus-like eruptions are known to be caused by occupational exposure to colour film developing agents that are derivatives of p-phenylenediamine (PPDA), e.g. CD-2 and CD-3. To elucidate whether such chemicals are a cause of lichen planus in patients at a department of general dermatology, 119 lichen planus patients were interviewed about occupational and non-occupational exposure to chemicals. Patch testing with CD-2, CD-3, PPDA and IPPD was performed in 49. No occupational risk group for lichen planus could be identified and no case of contact allergy to the tested substances was found. Patch testing with these substances is only recommended when there is a history of exposure.