Phototherapy is one of the main treatments for psoriasis. The most widely used modality today is narrowband UV-B radiation. In most dermatology departments, phototherapy is initiated based on the skin phototype; however, the authors of this study calculate the minimal erythema dose (MED), which often enables therapy to be initiated at higher doses and clinical results to be obtained sooner. Another advantage of calculating the MED before phototherapy is the possibility of identifying systemic photosensitivity.1 What is remarkable in this study is that patients treated with photosensitizing drugs did not have low MED values (according to the standardized values published by the Spanish Photobiology Group [Grupo Español de Fotobiología], which served as guidelines for the authors).2 Also noteworthy is the finding that patients with psoriasis were less likely to have a low MED. Given that psoriasis is the disease in which phototherapy is most widely used, calculation of baseline MED to reduce the number of light treatments would be recommendable and beneficial for a large number of patients with this disease.