Multiple chemical sensitivity (MCS) is an illness marked by multiple symptoms in multiple organ systems when exposed to chemicals at levels below what is expected to produce illness. It is also known as environmental illness (EI). MCS is fairly common in the U.S. population, with 16% of people in California and New Mexico reporting they were "unusually sensitive to everyday chemicals" and 6% and 2%, respectively reporting a prior MCS diagnosis.^1,2

Diagnosis of MCS
Consensus criteria for the definition of MCS were established by a group of MCS researchers and clinicians in 1999.³ The following six criteria must be present for a person to be diagnosed with MCS:

1. The symptoms are reproducible with repeated exposure to the same chemical.
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. Symptoms involve multiple organ systems (most commonly the neurological, immune, respiratory, skin, gastrointestinal and musculoskeletal).

The diagnostic criteria are not specific about the symptoms experienced by MCS patients. However, commonly reported symptoms include respiratory problems, headache and gastrointestinal distress.

Cigarette smoke, paint, gasoline, new carpet and furniture, household cleaners, perfume, newspapers, pesticides, alcohol, caffeine and food additives are some of the chemical exposures commonly cited as producing MCS symptoms.

MCS and CFIDS
Many chronic fatigue and immune dysfunction syndrome (CFIDS) patients report that their symptoms worsen when exposed to low levels of chemicals, especially when compared to pre-CFIDS. CFIDS patients also report worsening of allergies, which may be related to MCS.

Veterans of the Persian Gulf War report chemical sensitivities at a three-times higher rate than civilians or veterans who did not participate in the Gulf War.³ Persons with Gulf War illnesses (GWI) also have a three-fold increased risk of CFIDS compared to civilians or non-deployed veterans.⁴

Several studies have measured the overlap between CFIDS and MCS. In specialty clinics, between 13 and 88% of MCS patients meet criteria for CFIDS.⁵ In the general population of chronically fatigued people (which may be more representative of the CFIDS and MCS populations at large), 14% of MCS patients also had CFIDS and 41% of CFIDS patients met criteria for MCS.⁵ This study also found that people with more than one diagnosis were the most severely disabled -- the people most likely to be seen in a specialty CFIDS or MCS clinic.

Cause of MCS
The cause of MCS has not been identified. Some cases arise following a long-term, low-level exposure to a toxin, while others come on acutely after a short, high-level exposure. The body then becomes sensitive to other chemicals, a phenomenon known as "spreading." Research is being conducted to determine the cause(s) of MCS and its effects on the body.

Treatment for MCS
Treatment for MCS usually involves avoiding the chemicals that produce symptoms. This can be quite difficult, since chemicals are ever-present in modern life. The most severely affected find that they are virtually imprisoned in their homes (where they can more easily control substance exposures) due to the effects of MCS. Fortunately, most MCS patients aren't this severely affected, although they must still use extreme caution when encountering chemical exposures.

Patients must undergo a laborious process of finding out which chemicals must be avoided by first eliminating them from their environment and then introducing them, one by one, to test their effects. Since many MCS patients report food intolerances, an elimination diet can be very helpful in pinpointing particular food sensitivities.

It is often necessary for MCS patients to remove offensive materials (such as carpeting or stained cabinetry) and furnishings (such as old bedding and upholstered furniture) from their homes, replacing them with things that are made specifically for the chemically sensitive. This can be a costly and time-consuming process, but may help MCS patients can function to the best of their ability.

Some providers also recommend detoxification treatments, such as saunas. However, if you are one of the many CFIDS patients with orthostatic intolerance, use caution because warm environments are known to worsen those symptoms. Nutritional supplements and exercise are other treatments offered by MCS specialists.

References

1. Kreutzer R, Neutra RR, Lashuay N. Prevalence of people reporting sensitivities to chemicals in a population-based survey. Am J Epidemiol. 1999;150:1-12.
2. Voorhees RE. Letter to Joe Thompson, Special Counsel Office of the Governor. 13 March 1998.
3. Multiple chemical sensitivity: a 1999 consensus. Arch Environ Health. 1999;54:147-9.
4. Fukuda K, Nisenbaum R, Stewart G, et al. Chronic multisymptom illness affecting Air Force veterans of the Gulf War. JAMA. 1998;280:981-8.
5. Jason LA, Taylor RR, Kennedy CL. Chronic fatigue syndrome, fibromyalgia and multiple chemical sensitivities in a community-based sample of persons with chronic fatigue syndrome-like symptoms. Psychosom Med. 2000;62:655-63.