The skin microbiome plays a role in the pathogenesis of atopic dermatitis. However, it is unclear whether the range of microbiota on the skin is the cause or consequence of atopic skin inflammation.

The influence of new systemic therapies for the treatment of moderate to severe atopic dermatitis (such as biologics or Janus kinase inhibitors) on the skin microbiome is largely unknown.

The main aim of this scientific exploratory study is to investigate whether and how the skin microbiome changes in patients with moderate to severe atopic dermatitis during systemic therapy. This not only allows new hypotheses to be generated on the pathogenesis of atopic dermatitis, but also new objective scales for the severity of atopic dermatitis can be developed.

A better understanding of the pathology of atopic dermatitis could lead to the development of new therapeutic strategies for this disease and contribute to better and more targeted disease management - an advantage for all patients with atopic dermatitis.

The routine examinations are carried out every quarter with routine visits over two years. The dates before, 6, 12, and 24 months after the initiation of systemic therapy are relevant for this study. Deviations from normal practice are not intended.

Patients in whom a new initiation of systemic therapy is planned will be invited for a follow-up 6 weeks after initiation and quarterly follow-up visits.

Blood samples must be obtained for the examination. The blood is taken to determine the systemic level of inflammatory mediators (serological biomarkers, PBMCs) and for genetic examinations (e.g. filaggrin gene mutation - FLG) as well as mRNA / lncRNA profile. The skin physiological examinations are not invasive or pain-related procedures. Microbiome sampling will be conducted by a skin swab of the inter-scapular region.

The blood / skin samples taken as part of this scientific study are pseudonymized in the research laboratories. The samples are stored in the laboratories for a period of 5 years after the end of the study and then destroyed.

Inclusion Criteria:

• Patients with moderate to severe atopic dermatitis
• Indication for systemic therapy

Exclusion Criteria:

• Patients under 18 years of age upon introducing systemic therapy
• Pregnant and lactating women

Consecutive patients with moderate to severe atopic dermatitis presenting in the clinic of Dermatology, Charité - Universitätsmedizin Berlin, Germany.