multiple chemical sensitivity (MCS), adverse physical reaction to certain chemicals in susceptible persons. When exposed to the chemicals, people with MCS react with symptoms such as nausea, headache, dizziness, fatigue, impaired memory, rash, and respiratory difficulty. A wide range of household and industrial chemicals, including cleaning products, tobacco smoke, perfumes, inks, and pesticides, have been implicated as triggers for MCS.
Many researchers do not regard multiple chemical sensitivity as a medically valid syndrome, believing that the depression that frequently accompanies it is an indication that the symptoms are psychological in origin. Others note that descriptions of the syndrome are largely anecdotal and not proven scientifically, or that the imprecisely defined syndrome is easily abused as a diagnosis, pointing to what they feel is an exaggerated number of worker's compensation cases involving MCS. Nevertheless, many sufferers do seem to improve when they eliminate contact with the chemicals known to trigger their condition; in extreme cases this may mean confinement to specially treated living quarters.