Multiple Chemical Sensitivity - Definition

Definition

Six consensus criteria were identified by researchers for the diagnosis and definition of MCS in 1989 (later edited in 1999):

1. Symptoms are reproducible with repeated (chemical) exposures.
2. The condition has persisted for a significant period of time.
3. Low levels of exposure (lower than previously or commonly tolerated) result in manifestations of the syndrome (i.e. increased sensitivity).
4. The symptoms improve or resolve completely when the triggering chemicals are removed.
5. Responses often occur to multiple chemically unrelated substances.
6. Symptoms involve multiple-organ symptoms (runny nose, itchy eyes, headache, scratchy throat, ear ache, scalp pain, mental confusion or sleepiness, palpitations of the heart, upset stomach, nausea and/or diarrhea, abdominal cramping, aching joints).

The National Institute of Environmental Health Sciences (a division of the NIH) defines MCS as a "chronic, recurring disease caused by a person's inability to tolerate an environmental chemical or class of foreign chemicals". MCS has also been described as a group of "sensitivities to extraordinarily low levels of environmental chemicals" appearing "to develop de novo in some individuals following acute or chronic exposure to a wide variety of environmental agents including various pesticides, solvents, drugs, and air contaminants", including those found in sick buildings.

Environmental medicine specialists claim MCS causes negative health effects in multiple organ systems, and respiratory distress, seizures, cognitive dysfunction, heart arrhythmia, nausea, headache, and fatigue can result from exposure to levels of common chemicals that are normally deemed as safe.