Study of Methotrexate Efficacy Versus Cyclosporine in Moderate to Severe Atopic Dermatitis Patients

Inclusion Criteria: * Patients aged \> 18 years old. * Both genders eligible for study. * Moderate to severe AD. * Scorad \> 15. * Participants must use a contraceptive method during the trial and for 3 months after the end of the trial for female and 5 months for male participants. * Participants must be able to understand and sign the Informed Consent, and comply with all aspects of the protocol. * Patients must be registered in a social security system or with a health insurance coverage. Exclusion Criteria: * Pregnant or lactating women. * Evolutive skin disease. * Patients with a clinically significant disease (chronic, recurrent or active). * Systemic corticotherapy or immunosuppressive treatment during the previous month, or local corticoid the week before the inclusion. * Contra-indication to methotrexate and cyclosporine. * Exposure to phototherapy: cumulative dose \> 2000 J/cm2. * Patients deprived of their civic rights, in custody, or subject to a tutorial, judiciary or administrative decision. * Patients under a protection measure. * Patients in a critical medical situation. * Patients with a personal situation evaluated by the investigator as unable to give optimal participation to the study, or where the study could constitute a risk for the patient.