Koebner's Phenomenon in Psoriasis and Lichen Planus

Psoriasis and lichen planus often occur at mechanically irritated skin sites (e.g. tight clothing). The investigators would like to investigate this phenomenon in more detail in this study. For this purpose, the skin is specifically irritated at a small and cosmetically favorable site by tearing off scotch tape or rubbing with a wooden spatula. In order to be able to examine the inflammatory processes caused by the irritation more closely, a small skin sample and a skin swab are taken from the irritated area. This skin sample and the swab are repeated after three and fourteen days.