- Photo-sensitizing medication (e.g. psoralen, tetracycline, nalidixic acid, furosemide, amiodarone, phenotiacine, chinclone, fibrates, hypericumperforatum, arnica, valerian, tar, psoralen, ketoprofen) or colours (e.g. thiazide, toluidine blue, eosin, methylene blue, rose Bengal, acridine)