We conducted a prospective study aimed at investigating the prognostic value of the dynamic of a-GVHD progression from cutaneous to visceral involvement. In 108 consecutive patients who underwent allogeneic HSCT, we classified a-GVHD according to a “GHVD skin dynamic”: 18/82 patients started Corticosteroid (CS) within 48 h (Group 1); 13/82 started CS within days 3–7 (Group 2); Group 3A (n 31) was defined when Skin GVHD Overall Grade 1, left untreated for 1 week, showed an increase in involved body surface area <5 %; Group 3B (n 20), was defined when Skin GVHD Overall Grade 1, left untreated at 1 week, had an increase in involved body surface area >5%. These four groups had distinctive 2-y OS. Patients could be then grouped into “poor risk” (Group 1 and Group 3B) and “good risk” (Group 2 and Group 3A). “Poor risk” had inferior OS in univariate and multivariate analysis, (HR 2.222; 95% CL: 1.017–4.855; p 0.04). Among the patients with skin-only Grade 1 GVHD, subgroup 3A had an OS of 75.1% versus 39.8% found in subgroup 3B (p = 0.03). The dynamic of skin GVHD may be used to classify a-GVHD and guide treatment in Overall Grade 1 skin-only GVHD.