Eosinophilia Myalgia Syndrome (EMS; diagnostic code 710.5) is a systemic, immune mediated disease that originally surfaced in the United States as an epidemic in 1989. EMS resulted from ingestion of an amino acid, L-Tryptophan, a popular health food supplement at the time. The FDA recalled the supplement in March 1990.

Often, EMS is highly debilitating and can cause permanent damage. Because there is no cure and the prognosis is unknown, EMS is treated symptomatically.

During the acute phase, EMS is characterized by flu-like symptoms, intense muscle pain with spasms and contractures, burning rashes, breathing difficulties and elevated eosinophil (a type of white blood cell) count. Later the disease attacks many areas of the body in a random manner and with varying degrees of severity from patient to patient. Systems injured often include the neuromuscular, cardiopulmonary, gastrointestinal, dermatologic and endocrine systems among others. Since patients are treated symptomatically, physicians employ individualized treatment regimens.