Multiple Chemical Sensitivity:
A Spurious Diagnosis
Stephen Barrett, M.D.
The expression "multiple chemical sensitivity" ("MCS") is used to describe people with numerous troubling symptoms attributed to environmental factors. Many such people are seeking special accommodations, applying for disability benefits, and filing lawsuits claiming that exposure to common foods and chemicals has made them ill. Their efforts are supported by a small cadre of physicians who use questionable diagnostic and treatment methods. Critics charge that these approaches are bogus and that MCS is not a valid diagnosis.
What Is MCS?
The concepts underlying MCS were developed by allergist Theron G. Randolph, M.D. (1906-1995), who asserted that patients had become ill from exposures to substances at doses far below the levels normally considered safe. In the 1940s, he declared that allergies cause fatigue, irritability, behavior problems, depression, confusion, and nervous tension in children.
In the 1950s, Randolph suggested that human failure to adapt to modern-day synthetic chemicals had resulted in a new form of sensitivity to these substances. His concern with foods then expanded to encompass a wide range of environmental chemicals. Over the ensuing years, the condition he postulated has been called allergic toxemia, cerebral allergy, chemical sensitivity, ecologic illness, environmental illness (EI), immune system dysregulation, multiple chemical sensitivity, total allergy syndrome, total environmental allergy, total immune disorder syndrome, toxic response syndrome, 20th century disease, universal allergy, and many other names that suggest a variety of causative factors. These labels are also intertwined with Gulf War syndrome, sick building syndrome, toxic carpet syndrome, and other politically controversial diagnoses.
The complaints associated with these labels include depression, irritability, mood swings, inability to concentrate or think clearly, poor memory, fatigue, drowsiness, diarrhea, constipation, dizziness, mental exhaustion (also called "brain fog" or "brain fag"), lightheadedness, sneezing, runny or stuffy nose, wheezing, itching eyes and nose, skin rashes, headache, chest pain, muscle and joint pain, urinary frequency, pounding heart, muscle incoordination, swelling of various parts of the body, upset stomach, tingling of the fingers and toes, and psychotic experiences associated with schizophrenia. William J. Rea, M.D., who says he has treated more than 20,000 environmentally ill patients, states that they "may manifest any symptom in the textbook of medicine."
MCS proponents suggest that the immune system is like a barrel that continually fills with chemicals until it overflows and symptoms appear. Some also say that a single serious episode of infection, stress, or chemical exposure can trigger "immune system dysregulation." The alleged stressors include practically everything that modern humans encounter, such as urban air; diesel exhaust; tobacco smoke; fresh paint or tar; organic solvents and pesticides; certain plastics; newsprint; perfumes and colognes; medications; gas used for cooking and heating; building materials; permanent press and synthetic fabrics; household cleaning products; rubbing alcohol; felt-tip pens; cedar closets; tap water; and even electromagnetic forces.
There is no known mechanism whereby low levels of such varied substances can cause similar reactions involving multiple organ systems. Moreover, if the "total body load" concept were valid, the "sum" of small amounts of many unrelated chemicals (as well as infections and psychological stresses) would have the same effects as massive doses of single chemicals—which is not true. Like drugs, chemicals have specific effects whose development and severity depend on the amounts to which individuals are exposed.
Most physicians who diagnose and treat MCS identify themselves as "clinical ecologists" or "specialists in environmental medicine." About 400 of them belong to the American Academy of Environmental Medicine (AAEM, which Randolph founded in 1965 as the Society for Clinical Ecology, is composed mainly of medical and osteopathic physicians. Clinical ecologists also play a significant role in the American Academy of Otolaryngic Allergy (AAOA), which Randolph helped found in 1941.
Clinical ecology is not a recognized medical specialty. Environmental medicine and occupational medicine are components of the specialty of preventive medicine, but the theories and practices of clinical ecology are not. Critics of clinical ecology charge that: (a) MCS has never been clearly defined, (b) no scientifically plausible mechanism has been proposed for it, (c) no diagnostic tests have been substantiated , and (d) not a single case has been scientifically validated. The theories and practices of clinical ecology have been severely criticized by the American Medical Association , the American College of Physicians , the Canadian Psychiatric Association, the International Society of Regulatory Toxicology and Pharmacology , the American Academy of Allergy, Asthma and Immunology , the American College of Occupational and Environmental Medicine , and several prestigious scientific panels that have investigated them. In 1997, the academy's board of directors reviewed the evidence again and concluded that "a causal connection between environmental chemicals, foods, and/or drugs and the patient's symptoms is speculative and not based on the results of published scientific studies." 
Dubious Diagnosis and Treatment
Ronald E. Gots, M.D., Ph.D., who has reviewed the medical records of more than a hundred MCS patients, describes MCS as "a label given to people who do not feel well for a variety of reasons and who share the common belief that chemical sensitivities are to blame. He further states: "It defies classification as a disease. It has no consistent characteristics, no uniform cause, no objective or measurable features. It exists because a patient believes it does and a doctor validates that belief." 
The fact that MCS has not been meaningfully defined does not deter clinical ecologists from diagnosing it—typically in all or nearly all of their patients. Their diagnostic evaluation usually includes an "ecological oriented history," a physical examination, and laboratory tests. The history-taking procedure may include a lengthy questionnaire that emphasizes dietary habits and exposure to environmental chemicals. The nature and purpose of the physical examination is unclear because no combination of physical findings can establish the diagnosis. Standard allergy test results are often normal.
The test clinical ecologists consider most important is called provocation-neutralization. During this procedure, the patient is asked to report any symptoms that develop after various concentrations of suspected substances are administered under the tongue or injected into the skin. If symptoms occur, the test is considered positive and various concentrations are given until a dose is found that "neutralizes" the symptoms. A variety of other chemicals, hormones, food extracts, and other natural substances may be prescribed as "neutralizing" agents.
"Neutralization" superficially resembles the desensitization process used by allergists. However, allergists test and treat with substances that produce measurable allergic responses, whereas clinical ecologists base their judgments on subjective responses.
Elimination and rotation diets may be used with the hope of identifying problematic foods. Single-food challenges may also be used. In severe cases, Rea's patients may spend several weeks in an environmental care unit (ECU) intended to remove them from exposure to airborne pollutants and synthetic substances. After fasting for several days, these patients are given "organically grown" foods and gradually exposed to environmental substances to see which ones cause symptoms to recur.
Many clinical ecologists use tests related to immune function or exposure to specific chemicals. Samples of blood, urine, fat, and hair may be examined for various environmental chemicals. Other blood tests may assess immunoglobulins, other immune complexes, lymphocyte counts, and "antipollutant enzyme" levels. Some of these tests lack an accepted protocol and have not been standardized, and none has been demonstrated to have a consistent pattern of alteration in MCS patients.
Some treatments are based on blood tests that can detect chemicals in concentrations of parts per billion. This enables levels too low to be clinically significant to be misinterpreted as evidence of unusual and harmful chemical exposure. If any "toxin" level is interpreted as abnormal, the patient will be advised that "detoxification" or "purification" can wash the undesirable chemicals from the body. The regimens may include exercise, sauna treatments, showers, massage, herbal wraps, megavitamin therapy (usually including several grams of niacin per day), self-administered "desensitization" injections, and the use of water and air purifiers.
The provocation-neutralization test was conclusively debunked by a study performed in the early 1980s by researchers at the University of California. The tests took place in the offices of clinical ecologists who had been treating the patients. During three-hour sessions, the patients received three injections of suspected food extracts and nine of normal saline. Sixteen patients were tested once, and two were tested twice. In nonblinded tests, these patients had consistently reported symptoms when exposed to food extracts and no symptoms when given saline injections. Under double-blind conditions, however, they developed symptoms with 16 of 60 food-extract injections (27%) and 44 of the 180 (24%) salt-water injections. The symptoms elicited by both types of injections were identical and included itching of the nose, watery or burning eyes, plugged ears, a feeling of fullness in the ears, ringing ears, dry mouth, scratchy throat, an odd taste in the mouth, tiredness, headache, nausea, dizziness, abdominal discomfort, tingling of the face or scalp, tightness or pressure in the head, disorientation, difficulty breathing, depression, chills, coughing, nervousness, intestinal gas or rumbling, and aching legs. The results clearly demonstrated that the patients' symptoms were placebo reactions. The study also tested the claim that "neutralizing" doses of offending allergens can relieve the patient's symptoms. All seven patients who were "treated" during the experiment had equivalent responses to extracts and saline .
Psychologist Herman Staudenmayer, Ph.D., of Denver, Colorado, has treated "MCS" patients for more than 30 years. He believes that although some people are very sensitive to various microorganisms, noxious chemicals, and common foods, there is no scientific evidence that an immunologic basis exists for generalized allergy to environmental substances. During the 1990s, like Rea, Staudenmayer and his colleague—the late John C. Selner, M.D. (an allergist)—used an environmental chamber to test sensitivity to airborne chemicals. However, they rejected clinical ecology theories and practices. Using well-designed double-blind tests, they demonstrated that "universal reactors" may develop multiple symptoms in response to the testing process without being allergic to any of the individual substances administered. One of their reports describes how they used an environmental chamber to evaluate 20 patients with multiple symptoms attributed to chemical hypersensitivity. These patients believed that they were reactive or hypersensitive to low-level exposure to many chemicals. Some had previously been evaluated and managed by clinical ecologists and diagnosed with "MCS." During nonblinded tests, these patients consistently reported symptoms they had associated with exposure at work, at home, or elsewhere. The environmental chamber enabled the patients to encounter measured amounts of purified air, compressed gasses, and air containing specific chemical concentrations, without knowing which situation was which. None of the patients demonstrated a response pattern implicating the chemicals supposedly responsible for their symptoms. Eighteen reported no symptoms at least once when the suspect chemical was present. Fifteen reported symptoms at least once when the suspect chemical was absent . In other words, patients reacted to their feelings and beliefs about the test, rather than to the substance in question .
In 1999, the American Health Foundation's Environmental Health and Safety Council reached a similar conclusion. After reviewing the evidence for various alleged mechanisms though which odor-bearing chemicals might cause MCS symptoms, the council concluded:
In no case was there persuasive evidence that any olfactory mechanism involving fragrance underlies either induction of a sensitized state or the triggering of MCS symptoms. Fragrances and other odorants could, however, be associated with symptoms as claimed by MCS symptomatics, because they are recognizable stimuli, but fragrance has not been demonstrated to be causal in the usual sense. 
A more recent study tested whether "MCS" patients could reliably distinguish between airborne solvents and placebo and whether there were significant differences in measurable biological and neuropsychological parameters between solvent and placebo exposures. During the study, 20 MCS patients and 17 controls underwent six sessions in a challenge chamber in which they were exposed to solvent fumes and clean air in random order. Neither the patients nor the experimentors knew which exposures were which at the time they took place. No differences accuracy in identifying chemical exposure were found between the two groups. Nor was cognitive performance influenced by solvent exposure or different between the groups. Nor was there any difference between the groups in serum cortisol levels measured before and after exposures .
The treatment clinical ecologists offer is as questionable as their diagnoses. One observer has commented that the variety of treatments they prescribe "seems limited only by their imagination and resourcefulness." The usual approach emphasizes avoidance of suspected substances and involves lifestyle changes that can range from minor to extensive. Generally, patients are instructed to modify their diet and to avoid such substances as scented shampoos, aftershave products, deodorants, cigarette smoke, automobile exhaust fumes, and clothing, furniture, and carpets that contain synthetic fibers. Extreme restrictions can involve wearing a charcoal-filter mask, using a portable oxygen device, staying at home for months, or avoiding physical contact with family members. Many patients are advised to take vitamins, minerals, and other dietary supplements. "Neutralization therapy," based on the results of provocative tests, can involve administration of chemical extracts under the tongue or by injection.
MCS patients typically portray themselves as immunologic cripples in a hostile world of dangerous foods and chemicals. In many cases, their life becomes centered around their illness. Various companies cater to these beliefs by offering such items as "organic" foods; odor-free personal products; special clothing, household products, and building materials; and even specially outfitted travel trailers. A recent article in Reason described how one woman wore a protective mask while shopping and another woman hung her mail on a clothesline for weeks before reading it, to allow the "toxins" in the ink to dissipate.
Many experts have studied "MCS" patients and concluded that their basic problem is psychologic rather than physical. The best current data suggest that certain psychologic factors predispose individuals to develop symptoms and to seek out someone who will provide a "physical" explanation of their symptoms. Many of these patients suffer from somatization disorder, an emotional problem characterized by persistent symptoms that cannot be fully explained by any known medical condition, yet are severe enough to require medical treatment or cause alterations in lifestyle. Some are paranoids who are prone to believe that their problems have outside causes. Others suffer from depression, panic disorder, agoraphobia, or other anxiety states that induce bodily reactions to stress. Many patients are relieved when a clinical ecologist offers what they think they need and encourages them to participate actively in their care. However, the treatment they receive may do them far more harm than good.
In 1986, Abba I. Terr, M.D., an allergist affiliated with Stanford University Medical Center, reported on 50 patients who had been treated by clinical ecologists for an average of two years. Most of these patients had made a workers' compensation claim for industrial illness. Their treatments included dietary changes (74% of the patients), food or chemical extracts (62%), an antifungal drug (24%), and oxygen given with a portable apparatus (14%). Fourteen of the patients had been advised to relocate to a rural area, and a few were given vitamin and mineral supplements, gamma globulin, interferon, female hormones, and/or oral urine. Despite treatment, 26 patients reported no lessening of symptoms, 22 felt worse, and only 2 had improved .
In 1989, Terr reported similar observations on 90 patients, including 40 covered in the previous report. He also noted that 32 of the 90 patients had been diagnosed as suffering from "Candidiasis hypersensitivity"—a fad diagnosis considered "speculative and unproven" by the American Academy of Allergy and Immunology .
Psychiatrist Donald W. Black, M.D., and colleagues at the University of Iowa College of Medicine have described how the misdiagnosis involved can produce psychosocial, financial, occupational, and psychological complications . The psychosocial complications usually stem from recommendations to avoid contact with offending agents. As a result, patients become socially constricted or reclusive. The financial cost can be enormous; for example, a patient may be instructed to add a "safe" room to his house, or rebuild his house according to EI principles. Relocating can be enormously expensive, particularly if it involves quitting one's job or moving long distances to seek a pollutant-free environment. Occupational complications can arise when a person is advised to quit a job or stop working, due to presumed exposure on the job.
A court case illustrates what can happen when the patient's true problem goes untreated. In 1991, a jury in New York City awarded $489,000 in actual damages and $411,000 in punitive damages to the estate of a man who committed suicide at age 29 after several years of treatment by a clinical ecologist in New York City. Testimony at the trial indicated that the patient was a paranoid schizophrenic who thought "foods were out to get him." This type of mental problem may respond well to antipsychotic medication. However, the testimony indicates that the doctor had diagnosed the man as a "universal reactor" and advised that, to remain alive, he must live in a "pure" environment, follow a restrictive diet, and take dietary supplements .
Another serious problem is the disruption that occurs when family members disagree about the value of "ecological" treatment. In one case I know, a teenage girl troubled by fatigue was diagnosed as sensitive to foods, chemicals, and electromagnetic fields by clinical ecologists whose tests, treatments, and recommended household modifications cost $100,000 during a one-year period. Although the girl's condition worsened, she and her mother had complete faith in the treatment and wanted to continue it. The girl's father, who concluded that the treatment was futile, was forced to choose between continuing to pay for it or antagonizing his wife and daughter, whom he deeply loved. With great reluctance, he filed for divorce in order to protect himself against financial ruin.
MCS support groups have lobbied to persuade employers and government agencies to adopt policies that "accommodate employees and members of the public disabled by chemical barriers." One lengthy list of recommendations includes: (1) better ventilation systems; (2) no use of air fresheners; (3) no indoor use of pesticides except in emergencies; (4) no use of synthetic lawn chemicals near the workplace; (5) no smoking in or near the workplace; (6) purchase of the "least toxic/allergenic" building materials, office furnishings, equipment, and supplies; and (7) employee prenotification for "construction and remodeling activities and toxic cleaning activities such as the use of paints, adhesives, and solvents, carpet shampoos and floor waxes." Many MCS patients have demanded that their workplace be totally free of odors. MCS sufferers have also argued for prohibition of perfumes, colognes, and fragrant hygiene products in the workplace. However, there has been no ruling about whether such prohibition would be a reasonable accommodation.
Attempts to accommodate chemically sensitive people are often futile. The most publicized example is that of Ecology House, an eight-unit "safe house" constructed in San Rafael, California. HUD contributed $1.2 million toward the project's $1.8 million total cost. The tenants were selected by lottery from about 100 applicants around the country. Although the building was intended to be free of synthetic chemicals, most of the initial tenants said it still made them sick.
In 2000, the Environmental Protection Agency rejected a proposal to recognize MCS as a disease and to promote special acommodations for people who claim to have it. The proposal flew in the face of scientific knowledge and could have had serious legal and economic consequences .
"MCS" in Court
Many claims and lawsuits filed to collect workers' compensation and Social Security Disability. Even when the ruling body does not recognize MCS as a disease, it may disregard causation and award benefits to a plaintiff considered disabled by a somatization disorder or other psychological impairment.
Many lawsuits have been based on allegations that chemical exposures cause disease by injuring the immune system. This notion is supported by a network of clinical ecologists and others who misinterpret laboratory data to support claims that virtually any symptom can be caused by exposure to almost anything. They testify that the immune system can become overactive (leading to numerous symptoms) or suppressed (leaving the individual at risk for infection, cancer, rheumatoid arthritis, and other diseases). Some cases involve people who are not physically ill but are afraid that low-dose exposure to environmental chemicals has affected their immune system and may make them susceptible to cancer or other diseases in the future.
Legitimate cases exist where exposure to large or cumulative amounts of toxic chemicals has injured people. But in many of the cases described above, serious immune disorders are being alleged merely because laboratory testing has detected traces of a chemical in the body or has found a minor deviation from "normal" in some measure of immune function. Fortunately, a 1993 U.S. Supreme Court decision has strengthened the ability of judges to exclude unscientific testimony  and many have done so .
Both Rea and his long-time associate Alfred Johnson, D.O. have been disciplined by the Texas Medical board. In 2007, the board charged that Rea had (a) used pseudoscientific test methods, (b) failed to make accurate diagnoses, (c) provided "nonsensical" treatments, (d) failed to properly inform patients that his approach is unproven, (e) practiced in areas for which he has not been trained, and (f) represented himself as certified by a board that is not recognized by the American Board of Medical Specialties . The complaint against Johnson—also filed in 2002—called his treatment "nonsensical" and charged that his interpretation of tests and diagnostic conclusions related to a patient demonstrated "an obvious lack of understanding of basic immunology." 
Both cases were settled in 2010 with agreed mediated orders under which Rea and Johnson agreed to revise their informed consent forms. Rea's form must state that (a) his injections contain only an "electromagnetic imprint" of the agents in question, (b) the therapy is not FDA approved, and (c) the therapeutic value of the therapy is disputed. In addition, he must not start using any formulations that contain any amounts of substances classified as hazardous or carcinogenic by the U.S. Environmental Protection Agency or any other federal or state regulatory agency  The charges not related to informed consent were dropped as part of the settlement. During the investigation, Rea testified that a "car exhaust" solution he used for injections was so dilute that only an "electromagnetic imprint" of the original active substances remained .
Johnson, who operates Johnson Medical Associates in Richardson, Texas, was reprimanded, fined $4,500,ordered to take 32 hours of continuing medical education courses related to allergy and immunology, and required to provide ready access to patient records if the Board investigates him in the future . Johnson's Web site says that he is a fellow, former board member, and course director of the American Academy of Environmental Medicine.
In June 2015, AAEM's online directory listed 217 practitioners, 150 of whom were medical or osteopathic physicians licensed within the United States. Checking their licensing status, I found that at least 23 others had been subjected to regulatory action .
"Multiple chemical sensitivity" is not a legitimate diagnosis. Instead of testing their claims with well-designed research, its advocates are promoting them through publications, talk shows, support groups, lawsuits, and political maneuvering (such as getting state governors to designate a Multiple Chemical Sensitivity Awareness Week). Many are also part of a network of questionable legal actions alleging injuries by environmental chemicals.
Many people diagnosed with "MCS" suffer greatly and are very difficult to treat. Well-designed investigations suggest that most of them have a psychosomatic disorder in which they develop multiple symptoms in response to stress. If this is true—and I believe it is—clinical ecology patients run the risks of misdiagnosis, mistreatment, financial exploitation, and/or delay of proper medical and psychiatric care. In addition, insurance companies, employers, other taxpayers, and ultimately all citizens are being burdened by dubious claims for disability and damages. To protect the public, state licensing boards should scrutinize the activities of clinical ecologists and decide whether the overall quality of their care is sufficient for them to remain in medical practice.
- EPA Proposal to Legitimize "MCS"
- Propaganda Techniques Related to Environmental Scares
- Regulatory actions against AAEM member
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- Barrett S. An analysis of the National Environmental Justice Advisory Council Enforcement Subcommittee's Resolution #21 on multiple chemical sensitivity. Quackwatch, Aug 20, 2000.
- Daubert v. Merrell Dow Pharmaceuticals, Inc. 113 S. Ct. 2786 (U.S. 1993). [Full Text]
- Staudenmayer H. Environmental Illness: Myth and Reality. Boca Raton, FL: Lewis Publishers, 1998, pp 317-322.
- Complaint. In the matter of the complaint against William James Rea, M.D., Aug 24, 2007.
- Complaint. In the matter of the complaint against Alfed Raymond Johnson, D.O., Oct 22, 2007.
- Mediated agreed order. In the matter of the complaint against William James Rea, M.D.
- Deposition of William J. Rea, M.D. May 21, 2010, pp 130-131.
- Mediated agreed order. In the matter of the complaint against Alfed Raymond Johnson, D.O., March 1, 2010.
- Barfrett S. Regulatory actions against AAEM members. Quackwatch, June 26, 2015.
This article was adapted from A Close Look at Multiple Chemical Sensitivity, a detailed, referenced, 64-page booklet that can be read online free of charge or ordered from Quackwatch, Chathan Crossing Suite 107/208; 11312 US Highwaty 15-501 North; Chapel Hill, NC 27517. The price for the printed booklet is $3 postpaid to U.S. addresses and $8 for Canadian or overseas orders. A longer version is available in the book Chemical Sensitivity: The Truth about Environmental Illness, by Stephen Barrett, M.D., and Ronald E. Gots, M.D., Ph.D.
This article was revised on June 26, 2015.