Atopic dermatitis (AD) places significant burden not only on quality of life, but is also associated with considerable costs to healthcare systems. Diagnosis of AD may be challenging when it starts in adolescence or adulthood, and is further complicated as its manifestations are different from those generally seen in children. Accordingly, better definition of diagnostic criteria for adult onset AD is needed to avoid misdiagnosis and undertreatment in adult patients. To provide practical guidance for clinicians to reliably diagnose AD in adult patients, representatives from three Italian dermatology scientific societies [Italian Society of Dermatology and Venereology (SIDeMaST), Italian Association of Hospital Dermatologists (ADOI), Italian Society of Allergological, Occupational and Environmental Dermatology (SIDAPA)] carried out a joint consensus meeting to develop useful indications for improving diagnosis of moderate to severe AD in adult patients in routine clinical practice. The most representative criteria for morphological criteria, localization, clinical history, and differential diagnosis were identified by the experts. The most frequent clinical presentations are those on the flexural areas, hands, face/neck, and trunk, with itch and eczema as key manifestations. The diagnostic path defined herein can form a sort of 'check list' for physicians to adopt when evaluating patients with suspected AD, which can help in refining a diagnosis and refer the patient for specialist dermatological care. It is hoped that the practical guidance developed by the consensus group will help to improve outcomes, lower overall costs of care, and ameliorate the patient's quality of life, even though validation in a large cohort of patients is still needed.