Multiple chemical sensitivity (MCS) is a condition in which people experience a broad array of symptoms in reaction to exposure to trace amounts of common chemicals. Symptoms are most often triggered by odors, typically affect many systems, and can range from a runny nose to difficulty breathing and heart palpitations. The cause of this condition is unclear and there is no universal consensus on how to diagnose or treat it. MCS afflicts millions of Americans, although its prevalence is difficult to establish reliably. Theories of causation include both the physical and the psychogenic. This article begins with a case study, describes the current research on MCS, and offers recommendations to guide nurses when treating these patients in the hospital.