Drug-induced cutaneous phenotypes can act as early, bedside-visible clinical risk signals of systemic toxicity because the skin externalizes immune dysregulation, epithelial injury, and microvascular disturbance before organ-specific symptoms are obvious. This narrative review synthesizes peer-reviewed human evidence linking drug-related eruptions to systemic harm and actionable clinical decisions. We searched databases through January 2026 with citation chasing and organized findings using a morphology-anchored framework cross mapped to drug classes and mechanisms. High-risk patterns repeatedly signal urgent systemic risk: painful dusky or targetoid lesions with mucosal involvement and blistering/epidermal detachment require immediate culprit withdrawal and admission-level supportive care; widespread eruption with facial edema plus fever, lymphadenopathy, eosinophilia, or atypical lymphocytosis requires drug discontinuation and close monitoring for drug reaction with eosinophilia and systemic symptoms (DRESS). Research priorities include prospective validation of phenotypes as quantitative predictive risk signals, harmonized outcomes, reproducible imaging standards, and bias-aware digital implementation.