Immune checkpoint inhibitors (ICI) have revolutionized cancer therapy. Recent estimates suggest that up to 44.0% of all cancer patients are eligible to receive ICI, equating to more than 800,000 patients in 2020 alone. Dermatologic immune related adverse events to ICI are common, occurring in up to 72 percent of ICI patients. The heterogeneity of dermatologic irAEs suggest novel pathophysiologic pathways, yet published literature on these reactions is limited. Understanding the clinical and immunologic characteristics of these reactions is critical foundational knowledge for supporting patients through ICI therapy, which may impact the length and quality of their lives. Despite the diversity of reaction patterns, visible clinical specificity and easy access to affected tissues, deep phenotyping of the immune toxicity has been limited.  Most research in this field thus far has been single institution cohort studies, which have limitations in regards to power and generalizability. By developing a multi-institutional effort to better characterize dermatologic irAEs clinically, histologically and immunophenotypically, we will improve our understanding and subsequent care of our vulnerable cancer patients with dermatologic irAEs.