Multiple chemical sensitivity (MCS) is a chronic health condition involving adverse reactions to small amounts of chemicals that are generally regarded as safe. Named "environmental illness" in the late 1940s, MCS — also referred to as "total allergy syndrome," "twentieth-century disease," and many other appellations — is a growing health problem.

Many people have some chemical sensitivities; exposure to perfume or cigarette smoke often causes headaches, sore throats, and congestion in otherwise healthy people.

In 1992, the National Academy of Sciences estimated that 15 percent of the U.S. population has chemical sensitivities. More recent incidence studies place the number closer to 30 percent, or one third of the population.

In people with MCS, however, the individual experiences sensitivities to many, many chemicals and allergens, with the number and type often increasing over time—a phenomenon known as “spreading”—and the symptoms becoming more severe.

Although it is not known exactly why, people with MCS are severely sensitive to a range of common chemicals, such as those found in soap, perfume, cigarette smoke, paint, pesticides, automobile exhaust, clothing, and plastics.

Symptoms can be mild or severe (sometimes life-threatening), chronic or acute, immediate or delayed. Most people with the disorder can pinpoint an acute exposure or pattern of repeated low-level exposures to toxins that triggered the onset of symptoms. MCS is a progressive disease: once an individual is sensitized to one set of chemicals, continued exposures produce a spreading effect, causing the individual to become sensitized to previously tolerated chemicals. New or more severe reactions to "traditional" allergens—such as pollen, dust, and mold— and to foods is also common. The most widely reported problem in day-to-day living for people with MCS is fragrance chemicals. Fragranced products—perfume, aftershave, essential oils, and scented deodorant, detergent, fabric softener, and shampoo—cause symptoms for almost all people with MCS.

The most common sensitizers—initial triggers—appear to be pesticides (including insecticides, herbicides, and fungicides), new carpeting, “sick buildings,” and natural gas (frequently resulting in carbon monoxide poisoning).

Chemical exposures can cause immune, endocrine, and central nervous system damage. As a result, the physiological impact of MCS is diverse; respiratory, musculoskeletal, gastrointestinal, reproductive, and cerebral functions may all be affected. Common symptoms include, but are not limited to, asthma and nasal congestion, skin and vision problems, headache, sore throat, fatigue, nausea, joint and muscle pain, dizziness, mental confusion and poor concentration, insomnia, and anxiety.

More severe symptoms such as internal swelling, seizures, vomiting, and fainting also occur. Permanent neurological damage, called toxic encephalopathy, is often observable in the results of IQ tests and brain scans (such as MRIs and CAT scans) and in nerve-pain syndromes and loss of such functions as concentration, learning, and memory.

There is no known cure for MCS. The only widely accepted treatment is avoidance of chemical triggers. People with MCS who are able to avoid exposures and create a chemically safe environment in which to live are often able to obtain relief from some of their symptoms and, in some cases, may even reverse the course of the illness. Excerpts from “Multiple Chemical Sensitivity: A 1999 Consensus Definition”

For the complete article, see the May/June 1999 issue of Archives of Environmental Health, Vol. 54, No. 3, pp. 147–149. Or go to http://www.mcsrr.org.The publisher grants permission for the free reprinting and distribution of this statement. Six criteria were agreed upon by group of researchers and clinicians with experience in the study, evaluation, diagnosis, and/or care of adults and children with chemical sensitivity disorders.

Consensus Criteria for MCS

1. The symptoms are reproducible with [repeated chemical] exposure.
2. The condition is chronic.
3. Low levels of exposure [lower than previously or commonly tolerated] result in manifestations of the syndrome.
4. The symptoms improve or resolve when the incitants are removed.
5. Responses occur to multiple chemically unrelated substances.
6. [Added in 1999:] Symptoms involve multiple organ systems.

Further Reading on MCS • The Hidden Dangers of Fragrance. Environmental Health Coalition of Western Massachusetts. Send a self-addressed stamped envelope with a note requesting the brochure to: EHCWM, PO Box 187, Northampton, MA 01061-0187. • Bonnye Matthews, Chemical Sensitivity. Jefferson, NC: McFarland and Company, 1992. —An excellent account and explanation of the illness, written by a person with MCS, and with a ton of medical and scientific information. • Nicholas Ashford and Claudia Miller, Chemical Exposures: Low Levels and High Stakes. New York, NY: Van Nostrand Reinhold, 1991. —Considered by some to be "the book" on MCS. Thorough and thoroughly researched. • Sharon Wachsler, "Guide to Multiple Chemical Sensitivity Resources," —Ability Maine,

If your group is interested in having a free presentation on MCS, contact Linda at Boston Self Help Center, (617) 277-0080.