Inclusion Criteria:  Patients receiving treatment with any of the Food and Drug Administration (FDA) approved monoclonal antibodies that block CTLA-4, PD-1, PD-L1, or any combination thereof Patients recommended to undergo skin biopsy due to a clinical diagnosis of ICI-induced dermatitis as part of routine and standard clinical care are eligible Patients must be age 18 or older Eastern Cooperative Oncology Group (ECOG) performance status < 2 Measurable disease as per RECIST 1.1 Patients must be able to personally sign and date informed consent indicating that the patient has been informed of all pertinent aspects of the study are eligible  Exclusion Criteria:  Patients taking antibiotics or who plan to begin taking antibiotics Use of topical or systemic steroids within the past 14 days. Inhaled steroids are permitted Known medical condition (e.g. a disease associated with chronic skin inflammation such as atopic dermatitis or psoriasis) that, in the investigator's opinion, would increase the risk associated with study participation or interfere with the interpretation of results Not recovered to non-dermatologic =< grade 1 toxicities related to any prior therapy Pregnant woman will not be enrolled in this study. It is a regulatory requirement that for studies that carry no prospect of benefit to the woman, the research can only enroll pregnant women if the resulting knowledge cannot be obtained by any other means. In this study, there is no prospect of direct benefit to the pregnant women Patients with human immunodeficiency virus (HIV), hepatitis B, or C will be excluded from this study Any other condition that would, in the Investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns or compliance with clinical study procedures (including compliance issues related to feasibility/logistics)