At inclusion, 52.5 ml of blood will be collected, then an additional skin biopsy and a skin swab. Five questionnaires will be filled in by the patient.~At 6 months, then every years for 5 years, the same 5 questionnaires will be collected as well as the clinical data. However, no more biological samples will be collected.
Very little is currently known about the pathophysiology of pruritus sine materia according to the etiology. The creation of this cohort should make it possible to improve our clinical and biological knowledge according to the etiology, by collecting blood, skin, feces, and clinical data.