Non-Infectious Causes of Rash Mimicking Infectious Diseases: A Clinical Review for Undergraduate Medical Training

Rashes are among the most frequent reasons for consultation in primary care, pediatrics, dermatology, and emergency medicine. Clinicians often encounter patients presenting with erythematous, maculopapular, vesicular, or urticarial eruptions accompanied by fever or systemic symptoms. In routine practice, these presentations are commonly presumed to be infectious in origin—such as viral exanthems, bacterial toxin-mediated illnesses, or fungal and parasitic infections. However, a significant proportion of these rashes arise from non-infectious causes, including drug reactions, autoimmune diseases, allergic responses, nutritional deficiencies, and environmental exposures. These non-infectious dermatoses may closely mimic the morphology, distribution, and clinical course of infectious diseases, leading to diagnostic pitfalls.