Clinical efficacy of blue light full body irradiation as treatment option for severe atopic dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disease. Specific therapy of AD relies on topical or systemic immunosuppression and/or UV irradiation. In the present study, we assessed clinical efficacy and histopathological alterations induced by blue light treatment of AD within an observational, non-interventional study. 36 patients with severe, chronic AD resisting long term control of disease with topical corticosteroid interval treatment were included. Treatment consisted of one cycle of 5 consecutive blue light irradiations (28.9 J/cm2). Patients were instructed to ask for treatment upon disease exacerbation despite of interval therapy with topical corticosteroids. In the majority of patients, first signs of improvement were observed after 2-3 cycles. The clinical EASI score was improved by 41% and 54% after 3 and 6 months, respectively (p ≤ 0.005, and p ≤ 0.002). Significant improvement of pruritus, sleep and the Dermatology life quality index (DLQI) were noted especially after 6 months. In addition, the frequency and intensity of disease exacerbations and the usage of topical corticosteroids was reduced. Finally, immunohistochemistry of skin biopsies obtained at baseline and after 5 and 15 days revealed that, unlike UV light effects on skin, blue light treatment did not induce Langerhans cells/dendritic cell (DC) or T cell depletion from skin. In summary, our data strongly suggest that blue light irradiation may represent a suitable treatment option for AD providing long term control of disease. Future studies with larger patient cohorts within a randomized, placebo-controlled clinical trial are required to confirm this observation.