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Am Fam Physician. 1999;59(8):2101-2116

to the editor: The article, “Multiple Chemical Sensitivity Syndrome,” by Drs. Magill and Suruda1 omits reference to the recent joint consensus statement by the American Medical Association, the American Lung Association, the U.S. Environmental Protection Agency, and the U.S. Consumer Product Safety Commission.2 This statement concludes that multiple chemical sensitivity (MCS) should not be dismissed as psychogenic and recommends giving patients a thorough medical work-up.

The conclusion of this statement is supported by researchers at Johns Hopkins University who analyzed the current medical literature that supports a psychologic origin for MCS. Because all of the studies analyzed were found to have such serious methodologic problems, it was concluded that available evidence does not support a psychologic etiology for MCS.3

I am a physician practicing occupational medicine who cares for hundreds of patients with MCS. In my experience, reducing environmental exposure to exacerbating irritants and pollutants consistently results in the long-term reduction of symptoms. The effect of reducing exposures has also been documented in the medical literature.4 Furthermore, MCS is often accompanied by complications such as adrenal insufficiency; reduced secretory IgA with parasitic or other opportunistic infections; disturbances in energy metabolism; impaired detoxification usually involving phase II of the detoxification pathway; and numerous other biochemical, nutritional and endocrine impairments.

Quantification of symptoms in 100 new patients with MCS who were seen in my medical practice between January 1996 and January 1998 revealed that 88 percent met the diagnostic criteria of the Centers for Disease Control and Prevention for chronic fatigue syndrome and 49 percent met the diagnostic criteria of the American College of Rheumatology for fibromyalgia. The overlap between these syndromes has been documented elsewhere in the medical literature.5

Half of the medical literature on MCS has been written in the past five years; hundreds of articles are now available that discuss physiologic abnormalities in patients with MCS. A bibliography is available by writing MCS Referral and Resources, 508 Westgate Rd., Baltimore, MD 21229 or through their Web site (

MCS often develops after repeated symptomatic exposure to petrochemicals, combustion products or irritants. Common causes of MCS that are discussed in the medical literature include “sick building” exposure, exposure to pesticides (e.g., organophosphates, carbamates, pyrethroids, organochlorines), solvents, chemicals used in renovations and remodeling of buildings, adhesives, aldehydes, chlorinine dioxide and other halogenated irritants, and heavy frequent occupational exposure to carbonless paper.

A researcher from Johns Hopkins University developed a valuable screening instrument that evaluates the degree of response to various well-defined exposures. A copy is available through the 501 C3 nonprofit MCS Referral and Resources.

Based on my experience, family physicians who care for patients with MCS tend to provide more comprehensive care with better continuity and prevention, compared with “organ system specialists” who care for these patients. I encourage family physicians to continue expanding their role as sentinels to further scientific understanding of this major public health problem. Chronic illness accompanied by chemical sensitivity has been found in 3.8 to 6.3 percent of the population,6 with milder forms affecting 15 percent or more.

to the editor: We read with interest the article, “Multiple Chemical Sensitivity Syndrome,” by Drs. Magill and Suruda1 and the accompanying editorial by Dr. DeHart.2 We agree with Drs. Magill, Suruda and DeHart that evidence is insufficient to establish a relationship between allergy, toxic exposure and neurobiologic sensitization, and symptoms expressed by these patients.

As physicians who specialize in occupational medicine and medical toxicology, we frequently evaluate patients who are labeled as having multiple chemical sensitivity (MCS). In our clinical experience and ongoing review of the research concerning this issue, we believe that the term “idiopathic environmental intolerance,” which is recommended by the International Programme on Chemical Safety of the World Health Organization,3 is a more suitable name for this syndrome. MCS denotes an unsupported judgment on the relationship between chemicals and allergy. Since the etiology and underlying mechanisms4,5 of this syndrome have not been proven, idiopathic is a more suitable term. Furthermore, this syndrome has no validated clinical criteria for diagnosis; thus, “environmental intolerance” would better describe the condition.

As Dr. DeHart emphasizes in his editorial, physicians must not contribute to the patient's belief in chemical and social avoidance. In extreme situations, when social isolation becomes one of the psychologic defenses, patients are at risk for increased depression and suicidal ideation. In order to find a solution to this phenomenon, we physicians must adhere to the scientific method that is the foundation of biologic medicine.

to the editor: I strongly disagree with Drs. Magill and Suruda, the authors of “Multiple Chemical Sensitivity Syndrome,”1 that avoiding exposures to chemicals does not help patients with multiple chemical sensitivity (MCS). I do not believe that patients should be encouraged to work and socialize despite the symptoms and that it is possible to establish a respectful and empathetic physician–patient relationship when the physician does not acknowledge the patient's illness. I also do not agree that “standard treatment” should be provided for identified medical disorders in patients with MCS, since many of these patients cannot tolerate standard drugs or customary dosages. They often require nonpharmaceutical treatment or medications that are specially formulated to be free of preservatives, dyes, fillers and binders.

Far from being contraindicated, the avoidance of exposures to chemicals is the cornerstone of the treatment of MCS. Two polls of patients with MCS have shown that the overwhelming majority of respondents, 95 percent2 and 93 percent,3 reported that avoiding exposures to chemicals was either a major or enormous help in reducing symptoms. None of the 243 respondents in one study4 and only one of 305 respondents in the other study3 reported that this practice was harmful. Even an article that was referenced by Drs. Magill and Suruda states that “odors and exposure to volatile organic compounds in the workplace and home, which are perceived as irritating or noxious by the symptomatic person, should be reduced and controlled as much as possible.”4

In my practice, I have repeatedly witnessed the benefits of reducing exposures to chemicals. One of my patients is a 45-year-old corporate consultant who developed incapacitating confusion, headaches, insomnia, emotional lability and chemical sensitivities following a month-long exposure to mothballs containing naphthalene. She was instructed to move from her house and, after staying with a friend in a less contaminated environment for six months, she recovered to the point that she was able to go back to work.

By contrast, another of my patients was a school teacher who tried to keep working even though she was getting sick from the remodeling chemicals and pesticides that were being used at her school. Since her doctors told her that nothing was wrong with her and because she loved children and her job, she pushed herself to the point that she is now permanently disabled and unable to work.

Symptoms of MCS are not just irritating autonomic disturbances, such as those associated with stage fright, but often are caused by serious reactions such as malignant arrhythmias, asthma, seizures and anaphylaxis. Patients with MCS can no more ignore their symptoms than someone who is having an anaphylactic reaction to peanuts. Recently, one of my chemically sensitive patients was exposed to a neighborhood herbicide, which caused her to have protracted vomiting and eventually be hospitalized for upper gastrointestinal bleeding. Encouraging patients with MCS to slowly increase their exposures to chemicals in hopes that their reactions will go away is no more rational or ethical than having patients with diabetes slowly withdraw from insulin and attempt “to work and socialize despite the symptoms.”

to the editor: Multiple chemical sensitivity (MCS) is a serious, growing health problem that affects children and adults of all ages, races and economic backgrounds. We have seen an increasing number of such patients in our practice. Patients with MCS are made sick by exposures to many commonly encountered chemicals at levels that ordinarily do not affect other people. This condition may be distinguished from other illnesses by the fact that symptoms of MCS come and go in relation to various exposures to chemicals.

MCS is recognized as a potentially disabling condition by the Social Security Administration1 and the U.S. Department of Housing and Urban Development,2 and it is covered under the Americans with Disabilities Act3 on a case-by-case basis, as are all other conditions.

The authors of the article, “Multiple Chemical Sensitivity Syndrome”4 stated that “the incidence and prevalence (of MCS) are unknown,” but at least two states have obtained data on the prevalence of chemical sensitivities and the diagnosis of MCS. A 1995 California Department of Health Services Behavioral Risk Factor Surveillance Survey (BRFSS), a random population-based study, found that 15.9 percent of 4,000 respondents reported being unusually sensitive to chemicals, and 3.5 percent reported being diagnosed with MCS/environmental illness and being sensitive to chemicals, according to Richard Kreutzer, M.D., Acting Chief, Environmental Health Investigations Branch, California Department of Health Services (oral communication to Ann McCampbell, M.D., Chair, MCS Task Force of NM, January 8, 1997).

In a 1997 New Mexico BRFSS study, 17 percent of 1,814 respondents (21 percent of the women participants and 11 percent of the men participants) reported being unusually sensitive to everyday chemicals (such as those found in household cleaning products, paints, perfumes, detergents and insect sprays), and 1.9 percent reported that they had been diagnosed with MCS, according to Ron Voorhees, M.D., M.P.H., Deputy State Epidemiologist, New Mexico Department of Health (oral communication to Ann McCampbell, M.D., Chair, MCS Task Force of NM, January 28, 1998). The study also found that 2.1 percent of participants had lost a job or a career because of their chemical sensitivities. Respondents in New Mexico who reported chemical sensitivities were evenly distributed throughout the state. They were also evenly distributed among racial and ethnic groups, except among Native American respondents, of whom 31 percent reported being chemically sensitive.

to the editor: Dr. DeHart's editorial, “Multiple Chemical Sensitivity,”1 amply demonstrates and perpetuates the disdain that is commonly directed by the medical community toward patients with multiple chemical sensitivity (MCS). Physicians must realize that patients with MCS are not the enemy. Most physicians seem to be so worried that they will be “fooled” into thinking these patients are ill that they don't realize they have already been fooled in a much bigger way by a sophisticated disinformation campaign being waged by the chemical industry. This campaign is similar to the campaign used by the tobacco industry to deny the health hazards of its products. In my experience, information that strives to discredit people with MCS and cast doubt on the existence of the illness comes from industry nonprofit front groups, industry associations or physicians who work for the chemical industry, either as expert witnesses or in some other way.

In its 1990 Environmental Illness Briefing Paper,2 the Chemical Manufacturers Association (CMA) vowed to work to prevent the recognition of environmental illness (now called MCS) in order to preserve the profits of its member corporations. It also vowed to work with physicians, if necessary, to accomplish this. “Should environmental illness arise as an issue, a coalition with the state medical association is absolutely necessary.”2 The CMA's clearly stated goal is to block the recognition of MCS, not to learn the truth about it or to help those who have it.

I suspect most physicians do not realize that the pharmaceutical industry is part of the chemical industry, and that many of these companies make pesticides as well as pharmaceuticals. For example, CIBA-Geigy Corporation (now Novartis) makes the widely used herbicide atrazine; Novartis is also a large manufacturer of the organophosphate insecticide diazinon; Eli Lilly used to be part of DowElanco (now Dow AgroSciences), the largest manufacturer of another organophosphate insecticide, chlorpyrifos; and Bayer makes a popular pyrethroid insecticide, cyfluthrin. Hence, drug companies have a financial stake in blocking or distorting information about MCS, too.

In my opinion, pharmaceutical companies have been key in preventing physicians from obtaining accurate information on MCS through their influence on journal publications, conference proceedings, refusal to conduct research on MCS and lobbying to block research by government entities. In 1996, a CIBA-Geigy lobbyist traveled from another state to submit testimony to a New Mexico legislative committee opposing, among other things, funding for a prevalence study of MCS, the creation of an MCS information and assistance program, and an investigation into the problem of homelessness among people with MCS. Thus, the criticism that the pharmaceutical and chemical industries are impeding the necessary research, education and services needed by chemically sensitive people is not without merit.

The author complains that MCS “may become a disease by legal fiat” and that there is “a strong activist agenda.”1 Considering the abysmal response by the medical community to this burgeoning public health problem, it is not surprising that individuals who typically have lost their health, career, family, friends, income, home and independence due to MCS are dedicated to bringing attention to this illness in any way they can—both for themselves and to prevent others from getting sick. Rather than dismissing patient complaints as psychogenic, as is the author's implied suggestion, I urge the medical community to take a leadership role in demanding comprehensive research on MCS, providing accessible offices and hospitals for patients with MCS, and making a commitment to helping patients with this devastating illness.

in reply: The comments made by the letter writers illustrate a point we made in our article1: multiple chemical sensitivity (MCS) is a subject that elicits controversy and emotion. At no point in our article did we suggest, as was implied by Dr. Ziem, that the symptoms of MCS should be “dismissed as psychogenic.” Indeed, referring to the same article2 that Dr. Ziem cited in her letter, we said, “studies suggesting causality, rather than merely an association between MCS and psychiatric problems, are fraught with methodologic problems.” However, we also believe it would be unnecessarily cruel to withhold effective treatment for psychiatric illness, such as depression, when such illness is recognized in patients who are also living with MCS.

The article by Dr. Meggs and colleagues,3 cited by Dr. Ziem, assessed self-reported prevalence of “becoming sick after smelling chemical odors,” and the authors themselves cautioned that “this study was not designed to determine the prevalence of . . . the MCS syndrome.”

We have no doubt that some patients experience decreased symptoms with reduced exposure to irritants, as suggested in the quotation from an article by Dr. Sparks and colleagues4 that Dr. Elliott includes in her letter. However, there is a big difference between anecdotal experience and proof that reduced exposure to low-level pollutants eliminates the panoply of metabolic abnormalities described by Dr. Ziem. Indeed, it was the same article by Dr. Sparks that also stated, “recommendation for long-term avoidance of chemical exposures is contraindicated. It is also impossible to accomplish.”4

Dr. Elliott relies largely on anecdote and analogy to suggest benefit from avoidance of chemicals. The article to which she refers to support this assertion was a self-report study from a sample of patients with MCS, not a therapeutic trial.5,6 We do not believe that this is sufficient evidence on which to make such a disruptive therapeutic recommendation as extreme avoidance of low levels of chemical exposure for all patients suffering from MCS.

Drs. Gollub and Morton seem to imply that legal or regulatory recognition of a syndrome may substitute for scientific evidence of its etiology, and that unpublished data prove a substantial prevalence. We disagree.

Drs. Fung and Kennon object to our use of the name MCS. We chose this name because it is in common use and has a clear definition that, as we stated in the article, denotes no judgment about causality. While we have no fundamental quarrel with the use of the term “idiopathic environmental intolerance,” in our view this change of label without change in meaning is a distinction without a difference.

in reply: The juxtaposition of the two letters by Dr. McCampbell and Drs. Fung and Kennon illustrates the controversy associated with the phenomenon of multiple chemical sensitivity (MCS).

In her letter, Dr. McCampbell implies that most physicians are victims of a “sophisticated disinformation campaign” that is being waged by the chemical and pharmaceutical industries. Dr. McCampbell currently chairs the MCS Task Force of New Mexico.

Last fall, a draft report issued by the Federal Interagency Workgroup on MCS was released for public comment.1 The Workgroup found that no single, accepted case definition of MCS has been established and that proposed definitions all differ in key criteria. The Workgroup noted that MCS is currently a symptom-based diagnosis without laboratory tests to support it or agreed on clinical manifestations. Although a patient can have disabling symptoms, objective clinical or laboratory evidence of disease is often lacking. It is doubtful that the distinguished members of the Workgroup could, as a body, be compromised by an industrial disinformation campaign.

Dr. McCampbell suggests that there has been little research conducted and few articles on this topic. The phenomenon of MCS and related topics has received wide dissemination. In 1993, the Human Ecological Action League published a selective bibliography that cited approximately 600 articles related to MCS.2 On February 6, 1999, I searched the National Library of Medicine Database using the phrase “multiple chemical sensitivity” and found 96 citations in peer-reviewed journals since 1995.

Both the medical peer-review literature and the lay press have given MCS wide coverage. As early as 1989, the American College of Physicians reviewed the status of the literature on MCS and found it lacking; however, recommendations were made for implementing research methodologies.3

In 1991, I was the principal drafter of a position paper on MCS by the American College of Occupational Medicine (now the American College of Occupational and Environmental Medicine), which stated in part: “It is the position of the American College of Occupational Medicine that the Multiple Chemical Hypersensitivity Syndrome is presently an unproven hypothesis and current treatment methods represent an experimental methodology. The College supports scientific research into the phenomena to help explain and better describe its pathophysiological features and define appropriate clinical interventions. This research should adhere to established principles of scientific inquiry and the results submitted for publication in recognized peer reviewed journals.”4

The National Academy of Science has supported the need for MCS research since 1992.5 Modest research funding for MCS has been provided by both state and federal governments. The Veterans Administration has established three environmental referral centers and added several million dollars annually to their budget to support these centers.

Dr. McCampbell suggests that I dismiss these patients' complaints as psychogenic. Over the past decade, I have seen approximately 70 patients who had been diagnosed with MCS. Nine of these patients were diagnosed with organic disease, including multiple sclerosis, lupus erythematosus, isocyanates-induced asthma and farmer's lung. Several additional patients were diagnosed with psychosocial conditions that included panic disorder and conditioned response to odor. We were unable to provide a definitive diagnosis for many of the patients. In my experience, most physicians consider patients with MCS to be truly ill; the issues to be dealt with are diagnosis and causation.

In their letter, Drs. Fung and Kennon suggest substituting the name “idiopathic environmental intolerance” for the name “multiple chemical sensitivity.” I agree with the suggestion and have begun to use the phrase in my own practice. However, this substitution does not meet with universal acceptance, especially among some advocates of MCS.

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This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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