End of funding period.

Atopic dermatitis (eczema) is a complicated skin condition. In fact, it represents many different underlying problems. These include abnormalities in the skin barrier, the immune system and the ability to handle different bacteria. Despite many recent gains in the understanding of eczema, a lot needs to be learned. There is little evidence to select between some of the older treatments that are available now. Even the newest targeted therapy does not clear most patients' skin. In order to improve the understanding of eczema, how to treat it now, and to enable discovery of new treatments, the investigators plan to enroll patients into a large study at three centres in Canada (University of Toronto, McGill University and University of British Columbia). The study is called the Canadian Atopic Dermatitis Cohort for Translational Immunology and Imaging (CACTI). In this study, the investigators will collect data on how severe participants' eczema is and what treatments they use. For participants who give permission, the investigators will collect blood and skin biopsy samples to study the mechanisms underlying their disease. The investigators will test to see which form of phototherapy (Broadband or Narrowband Ultraviolet B phototherapy) works best for eczema in a randomized clinical trial. The investigators will also use advanced imaging techniques to visualize the skin.

This trial registry entry, including the description of the treatment arms and outcomes, refer to the nested BROadband vs Narrowband photoTherapy for Eczema clinical trial.

Inclusion Criteria:

1. Atopic dermatitis according to the Hanifin and Rajka criteria.
2. Validated Investigator Global Assessment score of 3 or 4 out of 4
3. Eczema Area and Severity Index (EASI) score ≥7.1
4. Moderate to severe disease as above despite an adequate trial of topical therapy.

Exclusion Criteria:

1. Treatment with phototherapy or oral systemic immune-modulating agents (cyclosporine, methotrexate, azathioprine, mycophenolate) less than 30 days before baseline.
2. Treatment with systemic biologic (dupilumab) or experimental therapeutic less than 90 days before baseline.
3. Current treatment with oral or intramuscular corticosteroids within 30 days prior to baseline. Topical, intralesional or inhaled corticosteroids are allowed.
4. Participating in a clinical trial assessing an investigational agent for atopic dermatitis (topical, systemic or device) within 90 days prior to enrollment.

The full protocol for the CACTI study and nested BRONTE trial will be made publicly available.

The anonymized participant-level dataset and statistical code for the BRONTE trial will be made available to qualified investigators upon request.