Biologics are approved for various dermatologic, allergic, rheumatic, and gastroenterologic inflammatory diseases, as well as for numerous malignancies. The dermatologic adverse events from treatment with biologics may resemble primary inflammatory diseases but differ in pathogenesis. In this article, we describe five different pathogenic mechanisms of dermatologic adverse events. By studying these mechanisms, we hope to gain valuable insights into the pathogenesis of primary inflammatory diseases. In addition, in this article, we provide recommendations for the treatment and management of the dermatological adverse events induced by biologics.