Systemic contact dermatitis (SCD) is a broad category of syndromes characterized by a variety of clinical presentations and offending agents. There exists general consensus that SCD and its subcategories are due to type IV (and less commonly type III) hypersensitivity reactions, in which a previously sensitized individual undergoes a cytotoxic CD8⁺ T-cell response upon systemic reexposure. There are various linked allergens, generally grouped into plants, foods, metals, and medications. Diagnosis is relatively successful through epicutaneous patch testing utilizing standard series and customized panels. Treatment consists of allergen avoidance diets as determined by clinical history and patch testing.