Inclusion Criteria:  Patients over 18 years old with psoriasis, with or without itching (pruritus). Presence of lesional and non lesional zones, in unexposed areas and surface area (outside the face and folds) large enough to allow the biopsies to be performed Patients who have given written consent  Exclusion Criteria:  Patients with physical or psychological incapacity to sign consent Patients not covered by the Social Security system Patients with topical treatments for psoriasis, Patients with systemic treatments for psoriasis, Patients allergic to lidocaine Patients over the age of majority who are subject to legal protection or who are unable to give consent Patients deprived of liberty by a judicial or administrative decision Pregnant women, parturients and breastfeeding mothers