4. Substantial history of environmental exposure to tainted rapeseed oil, vinyl chloride, L- tryptophan, bleomycin, trichoroethylene, or silica; PUVA therapy within 1 month of study drug initiation; concurrent interventional therapy that might independently influence outcome of trial, such as D-penicillamine, cyclosporine, methotrexate, interferon-γ or photopheresis; topical corticosteroids treatment affecting the selected area; cosmetics over the treatment area.