Phototherapy with narrow band (nb) ultraviolet B (UVB) is a safe and effective but time consuming treatment option for patients with widespread eczema. Despite efficacy we know little about how it works, and even less why some patients fail to respond. Tintle et al showed that nb-UVB induced strong suppression of the Th2 and Th22 axes in patients with atopic dermatitis (AD), and also normalized the epidermal barrier function. We want to map the very early changes in gene expression after UVB-treatment in order to shed light on disease mechanisms, which eventually could lead to better treatment options.

Patients will be scored with Patient-Oriented Eczema Measure (POEM), Eczema Area and Severity Index (EASI), SCORAD (SCORing Atopic Dermatitis) and Dermatology Life Quality Index (DLQI) to assess disease severity. The investigators will measure trans epidermal water loss (TEWL), take bacterial swabs for analysis of the microbiome and culture for Staphylococcus aureus and test for mutations in the filaggrin-gene by sputum samples. Blood serum samples will be taken to measure serum (s) -Immunoglobulin E, s-vitamin D status, full blood count including white cell differential and different cytokines. Any history of allergic asthma, allergic rhinitis or food allergy will be noted as well as any recent history of sun exposure, use of tanning beds or UVB-therapy.

The suberythemal dose of UVB for each patient will be established. In each patient two contralateral areas (e.g. both underarms) with eczema will be chosen, which are as similar as possible regarding distribution and severity. One area will be biopsied with a 4mm punch followed by locally treatment with nb-UVB (311nm) three times. In this way the untreated side will serve as an internal control. Both sides will be biopsied after these initial three rounds of treatment. The patients will then undergo 24 standard full-body nb-UV-treatment sessions followed by a new biopsy of the same area. Skin from non-lesional sun-protected skin from nates will also be samples prior to and after UVB-treatment.

Inclusion Criteria:

• Atopic dermatitis

Exclusion Criteria:

• Other inflammatory skin disease
• Concurrent illness