[1] Univ Hosp Regensburg, Dept Dermatol, D-93053 Regensburg, Germany
[2] Univ Regensburg, Inst Analyt Chem Chemo & Biosensors, Regensburg, Germany
[3] Clin Skin Allergy Phlebol & Environm Med, Recklinghausen, Germany
[4] Graz Univ Technol, Inst Analyt Chem & Food Chem, A-8010 Graz, Austria