Inclusion Criteria:  Confirmed diagnosis of PLE by typical patient history, typical histology of skin lesions and/or positive photo provocation test Healthy subjects  Exclusion Criteria:  Presence or history of malignant skin tumors; dysplastic melanocytic nevus syndrome Photosensitive diseases such as porphyria, chronic actinic dermatitis, xeroderma pigmentosum, basal cell nevus syndrome Autoimmune disorders such as lupus erythematosus or dermatomyositis Antinuclear antibodies titer over 1:160 within 12 months prior study Systemic treatment of steroids and/or immunosuppressive drugs within 4 weeks prior the study start Systemic treatment of antibiotics within the last 6 weeks prior study Local treatment of anti-microbial treatment in the test field area within the last 6 weeks prior the study Systemic treatment of medications/drugs/ that could affect inflammatory responses within 2 weeks prior study Allergy on tape strips and/or adhesive material Psychiatric disorders