Inclusion Criteria:  Patient diagnosed with non-segmental vitiligo (vitiligo) Vitiligo affecting more than 5% of the total body surface (vitiligo) Patient with unresectable stage III or stage IV skin melanoma confirmed histologically (melanoma) Treatment-naïve patient with an indication for anti-PD1 mono-immunotherapy with nivolumab or pembrolizumab regardless of their BRAF status (melanoma)  Exclusion Criteria:  Segmental or mixed vitiligo (vitiligo) Photodermatosis or taking a photosensitizing treatment (vitiligo) Patient being allergic to gluten (vitiligo) Melanoma of unknown origin (melanoma) Ocular melanoma or mucous melanoma (melanoma) Patient with brain metastases, symptomatic or not (melanoma) Disease not measurable according to RECIST 1.1 criteria (melanoma) Patient for whom a combination of anti-PD1 and anti-CTLA-4 immunotherapy is being considered. (melanoma) Active autoimmune disease: chronic inflammatory bowel disease and patients with autoimmune disease that is or has been symptomatic Patients with autoimmune motor neuropathy Concomitant intake of oral immunosuppressive therapy or topical corticosteroid therapy (on vitiligo lesions) or systemic Organ transplant patients (kidney, liver, lung, heart, etc.) Patient with a history of clinically significant allergy History of treatment with anti-CTLA-4, anti-PD-1 or anti-PD-L1, including in an adjuvant situation HIV and / or HCV and / or HBV positive serologies Patient's refusal to do an HIV, HBV, HCV serology Vulnerable people (minors, patients under guardianship or guardianship, deprived of their liberty, under the protection of justice, etc.) Patient participating or having participated in another clinical drug trial during the month preceding inclusion Women who are pregnant or breastfeeding or who planned to become pregnant during the course of the study.