Koebner's Phenomenon in Psoriasis and Lichen Planus (RENBOEK)

Inclusion Criteria: Dermatologist diagnosed psoriasis (group psoriasis), lichen planus (group lichen planus) or no skin disease (group healthy controls) Subject is capable of giving informed consent Signed informed consent Exclusion Criteria: Use of systemic immunosuppressive/immunmodulating agents in the last three months Use of topical anti-inflammatory treatment in the last 7 days in the area of sampling. Phototherapy in the last 4 weeks Active or recurrent serious bacterial, fungal or viral infection at the time of enrollment by patient history, including patients with Human Immunodeficiency Virus (HIV) infection, Hepatitis B and Hepatitis C infection, active or untreated latent tuberculosis. Female patients of childbearing potential who are pregnant or breast feeding or planning a pregnancy during the duration of the trial and/or not practicing acceptable birth control for the duration of the trial Known or suspected non-compliance, drug or alcohol abuse, Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant, Previous enrolment into the current study, Enrolment of the investigator, his/her family members, employees and other dependent persons.