Multicentric, placebo-controlled, double-blinded, three-armed, prospective, randomized controlled trial.150 patients diagnosed with atopic dermatitis will be randomized to arm 1 (irradiation for 30min at 415nm wavelength), arm 2 (irradiation for 30min at 450nm wavelength), and arm 3 (irradiation for 30min at low-dose (placebo)). Irradiation will be scheduled 3 times a week for 8 weeks. Patients will be followed up for four weeks after the last irradiation.

Inclusion Criteria:

• Signed and dated informed consent prior to any study mandated procedure
• Good health as determined by the Investigator
• Willing and able to comply with study requirements
• Atopic dermatitis (AD) fulfilling the United Kingdom (UK) criteria of AD
• Age between 18 and ≤ 75 years
• Reliable method of contraception for women of childbearing potential (i.e. low failure rate less than 1% per year; e.g. oral contraceptives, intrauterine device [IUD] or transdermal contraceptive patch)
• Willing to abstain from excessive sun / UV exposure (e.g. sunbathe, solarium) during the course of the study
• Body Mass Index ≥ 18 and ≤ 35

Exclusion Criteria:

General

• Inmates of psychiatric wards, prisons, or other state institutions
• Investigator or any other team member involved directly or indirectly in the conduct of the clinical study
• Participation in another clinical trial within the last 30 days
• Pregnant or nursing women
• Risk of non-compliance with study procedures

Medical History

• Past or present disease, which as judged by the investigator, may affect the outcome of this study. These diseases may include cardiovascular disease, malignancy, hepatic disease, renal disease, hematological disease, neurological disease, endocrine disease or pulmonary disease, and others.
• Clinically relevant abnormalities in hematology, or blood chemistry at screening.
• Positive HIV-1/2Ab, hepatitis B surface antigen (HBsAg) or hepatitis C virus antibodies (HCV-Ab) test at screening.
• Diastolic blood pressure above 95 mmHg.
• Febrile illness within 2 weeks prior to baseline visit.
• Alcohol or drug abuse within 12 months prior to screening (i.e., Regular daily consumption of more than 1 liter of beer or the equivalent quantity of approximately 40 g of alcohol in another form.)
• Photodermatosis and/or significant photosensitivity, including porphyria and/or hypersensitivity to porphyrins as well as photosensitivity due to present or past (within the last year) intake of amiodarone.
• Congenital or acquired immunodeficiency
• Patients who have been diagnosed with invasive skin cancer at any time (=malignant cells invaded below the basal membrane of the epidermis), or with severe actinic damage present at baseline visit.
• Patients with genetic deficiencies attached with increased sensitivity to light or increased risk to dermatologic cancer (i.e. Xeroderma pigmentosum, Cockayne Syndrome, Bloom-Syndrome).

Concomitant medication/treatment in medical history and during the study

Within 8 weeks prior to baseline visit:

• Systemic immunosuppression treatment (steroids, cyclosporine, azathioprine, Mycophenolate Mofetil (MMF))

Within 4 weeks prior to baseline visit:

• UV radiation treatment

Within 2 weeks prior to baseline visit:

• Topical steroid treatment
• Topical calcineurin inhibitor treatment

Within 3 days prior to baseline visit:

• Photo-sensitising medication (e.g. psoralen, tetracyclines, hydrochlorothiazide, phenothiazines, quinolones, hypericumperforatum, arnica, valerian, tar) as assessed by the regular medication plan of the patient
• colours (e.g. thiazide, toluidine blue, eosin, methylene blue, rose Bengal, acridine) which will be visible on the patient's skin

Patients are blinded by wearing tinted glasses for eye protection which disenable distinction of different wave lengths of light. Medical doctors will examine patients in other rooms than those equipped with the investigational medical devices. These examiners are blinded and are therefore not involved in the preparation and process of the irradiation.