Inclusion Criteria:  Written informed consent obtained from the subject prior to performing any protocol-related pro-cedures, including screening evaluations Age ≥ 18 years at time of study entry. Diagnosis of chronic atopic dermatitis for at least 1 year prior to enrollment based on American Academy Criteria Eczema Area and Severity Index (EASI) score ≥12 at baseline visit (Week 0) Investigator Global Assessment (IGA) ≥3 at baseline visit (Week 0) Subject is willing and able to comply with the protocol for the duration of the study Subject receives abrocitinib by the treating dermatologist within routine care  Exclusion Criteria:  1. Subject is unable to provide written informed consent or comply with the protocol Concurrent enrolment in another clinical trial where the subject is receiving an IMP or participation in another clinical trial with investigational product during the last 30 days before inclusion or 7 half-lives of previously used trial medication, whichever is longer. Active dermatologic conditions that may confound the diagnosis of AD or would interfere with as-sessment of treatment, such as scabies, cutaneous lymphoma, or psoriasis. Known active allergic or irritant contact dermatitis that is likely to interfere with the assessment of severity of AD. Having used systemic immunosuppressive/immunomodulating therapy (e.g. systemic corticoster-oids methotrexate, cyclosporine, azathioprine, mycophenolate mofetil, JAK inhibitors) or tanning beds or phototherapy during any week within the 4 weeks or receipt of any marketed biologic ther-apy (e.g., dupilumab, tralokinumab) within 3 months or 5 half-lives, whichever is longer, prior to baseline Treatment of selected marker skin areas (non-lesional skin at volar forearm and extensor forearm, lesional skin) with topical corticosteroid or topical calcineurin inhibitor 1 week prior to baseline visit and throughout the study. Treatment of skin areas of examination with emollients 24 hours prior to baseline visit and throughout the study. Involvement in the planning and/or conduct of the study.