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Multiple Chemical Sensitivity, MCS

2 History, definition, name, and delimitation in relation to other syndromes

2.1 MCS, development history
     2.1.1 Sensitivity in a toxicological context
     2.1.2 Disease, illness, syndrome
2.2 Description of MCS
     2.2.1 MCS symptoms
     2.2.2 MCS definition
     2.2.3 MCS, course
     2.2.4 MCS synonyms
2.3 Delimitation in relation to other syndromes and illnesses
2.4 Comments

2.1 MCS, development history

The allergologist Randolph (1952) was the first to report on a group of patients in the US, who experienced symptoms from chemicals in their daily surroundings, both at work and in their homes. He assumed that their symptoms were caused by a stress reaction due to exposure to organic compounds such as solvents, petrol, perfume, exhaust gasses, etc. Randolph and some of his colleagues published several new cases fitting to the description above.

The authors considered the illness to be a hypersensitivity reaction in accordance with the current broad definition of allergy of the 1950s and 1960s: An "intense" or "over"-reaction in one or more organs to an external stimulus, which in most people does not provoke a reaction. But many physicians and not least practicing allergologists and immunologists rejected this definition. They stuck to the narrower definition of the antigen-antibody-mechanism as (immunological) basis for hypersensitivity illnesses.

As a reaction to this rejection, Randolph, together with some like-minded colleagues, formed a new society for human ecology in 1965. He encouraged physicians of all medical fields to join the society. In 1985 the society became the "American Academy of Environmental Medicine" (AAEM) and its members were called clinical ecologists. The academy now has about 2000 members, 800 of which are oto-rhino-laryngologists. Even though the name of the academy includes concepts, which in Danish can be understood as environmental medicine, clinical ecologists from the US are not the same as Danish specialists in environmental medicine. Nor are environmental illnesses, which are diagnosed as such according to the definition of the AAEM, what Danish physicians regard as environmental illnesses.

In 1992 the academy presented their theory as a holistically oriented illness model for environmental illnesses, to which MCS belongs. According to this theory, many symptoms experienced by hypersensitive people arise from a functional disorder in one or more of the biological systems of the body (AAEM, 1992).

According to the AAEM, MCS has emerged because we are surrounded by an increasing number of potentially hazardous chemicals, which affect more and more people (see also Annex A).

The theories and concepts of the AAEM are described more thoroughly in section 6.6.

During the 1980s more and more accounts of MCS and other conditions and symptoms similar to MCS have emerged. The list of substances, which can elicit health complaints, has also grown considerably (see section 4.7).

Exposure to triggering causes can occur everywhere: In the home, at work, and out-of-doors.

Since 1990, MCS has been discussed increasingly in the US and Canada, among specialists as well as by the general public. The debate has included subjects as: MCS as a recognized illness, how it is defined and what causes it, the mechanism of illness, treatment, and the role of the authorities in relation to MCS. The unsolved problems relating to MCS have become more evident, e.g., through reference to them in the media and because MCS patients and their supporters have sought assistance from the authorities. Several ministries in the US government have been and are still involved in the debate, and they have funded a number of conferences and workshops.

Discussions concerning the ”Gulf War Syndrome”, which in many ways can be compared to MCS, have mobilised much support and many resources from high places in the US administration. In several US states and in some Canadian provinces MCS patients have been given compensation, and so-called ecological environmental health centres, where MCS patients are received and treated, have been established (see chapter 8).

Another historical perspective seems relevant as an introduction to this report. In a review article with many examples from history, Göthe (1995) describes how very different environmental factors for short periods of time have been focal points for new concepts of illness, which have led to epidemic-like spreading.

Table 2.1 Examples of environmental illnesses, historic review from the 19th and 20th centuries (Göthe, 1995)

Typical of the syndromes mentioned above is the fact that it has not been possible to detect objective functional or organic bodily changes. The symptoms are not specific and they resemble MCS symptoms. Most of the syndromes have disappeared in the course of a few years or decades.

2.1.1 Sensitivity in a toxicological context

Sensitive or sensitised people react more violently to a chemical when exposed to it a second time, than they did when they were exposed to it the first time. They also respond more violently at lower doses, which would not normally bother other people. Sensitivity is based on individual differences in susceptibility, where age, sex, genetic factors, other illnesses, previous exposure, and stress are decisive factors. In Denmark the word “intolerance” can be used instead of sensitivity.

2.1.2 Disease, illness, syndrome

Of the two English categories of sickness, disease (objectively measurable physiological and/or psychogenic change) and illness (a subjective state of discomfort which does not produce objectively measurable symptoms), MCS belongs to the latter. Some use the term syndrome, which is a condition with several subjective symptoms (signs of illness) or discomfort.

2.2 Description of MCS

The description most often used is the following:

"People who were previously well complain of repetitive non-specific symptoms which they ascribe to exposure to chemicals in very low concentrations."

MCS patients complain of good and bad odours. Odours originate from inorganic or organic chemicals.

2.2.1 MCS symptoms

The most frequently reported symptoms are listed in table 2.2.

Table 2.2 List of the most frequently reported MCS symptoms (Ashford & Miller, 1998)

Symptoms from various organs are shown in the left side of the table, and symptoms from the central nervous system (CNS) in the right side. According to the definition of MCS, all MCS patients have complaints from two or more organs. One of the organs is always the CNS. Many patients also show intolerance to alcohol (Vesterhauge, pers. com. 2001).

The reported MCS symptoms are not specific, that is they occur in connection with many other illnesses or syndromes.

2.2.2 MCS definition

The clinical definition of a disease is usually a combination of what the patient says and what an objective examination by a physician (physical examination) and laboratory analyses reveal. No objective changes are seen in connection with MCS. The definition of MCS is, therefore, solely based on observations made by the patient. They consist of the following criteria:

1. MCS starts in people who have previously considered themselves to be healthy.
2. The symptoms occur as a response to exposure to a certain chemical and they disappear, when this chemical is no longer present.
3. The patient complains of symptoms from more than one organ (two or more).
4. Symptoms can occur due to exposure to different non-related chemicals, which function via different toxic mechanisms.
5. It is possible to describe the situations of exposure, which bring about the symptoms.
6. Exposures, which bring about symptoms, involve very low concentrations; concentrations that are considerably lower than the average concentrations, which elicit health complaints in most people.
7. Other causes of illness can be excluded.

The bullet points listed above correspond to Cullen's (1987) criteria. These have been accepted by most of the international MCS scientists as the basis of common understanding and for co-ordinating further research.

Comments on the criteria:

According to several scientists, MCS starts after an initial exposure. This exposure can be a chemical exposure or a serious virus infection in an adult or it can be a traumatic event (Interagency, 1998; Graveling, 1999; Ashford & Miller, 1998). Some maintain that a psychogenic trauma can be the initial triggering event. This event is often a posttraumatic distress syndrome, which is a condition with symptoms of many different kinds following a serious accident.

It is important to underline that only few out of a group of people, exposed to the same chemical, develop the chemical sensitivity, which characterises MCS.

2.2.3 MCS, course

The condition lasts for several (more than two) years. Most people are never rid of the symptoms. Some patients experience symptoms daily. Others do so more rarely, perhaps once a week. A few have been found to lose their chemical sensitivity, enabling them once more to tolerate chemical odours in low concentrations.

Many patients react to an increasing number of chemicals and the number of symptoms also increase with time.

2.2.4 MCS synonyms

MCS has been given many names, especially in the English-speaking part of the World (see table 2.3). Most researchers use a name, which expresses their perception of cause, mechanisms or condition (result). The table gives a good representation of the differences and uncertainties in the perception of MCS among all groups dealing with the syndrome.

Table 2.3 Expressions describing conditions similar to Multiple Chemical Sensitivity.
The names are grouped according to cause, mechanism and result in relation to the mechanism of illness (from Ashford & Miller, 1998)

The condition has no official Danish name. In occupational medicine the term odour hypersensitivity is used.

A research team at the Copenhagen University Hospital (Rigshospitalet)National Hospital of Denmark has used the term acquired intolerance to organic solvents (Gyntelberg, 1986). In Sweden, the following names are used: multiple chemical hypersensitivity, multiple hypersensitivity, and environmental somatization syndrome (Ørbæk, 1998; Göthe, 1995; Lindelöf, 2000). In Germany MCS is called Chemikalienunverträglichkeit (chemical intolerance) (Maschewsky, 1998).

The American College of Occupational and Environmental Medicine is the forum in the US with most MCS experts. In 1999 it recommended the use of the name "idiopathic environment-related intolerance (IEI)" instead of MCS. The new name corresponds better with the present knowledge or lack of knowledge concerning the condition (ACOEM, 1999). Idiopathic implies that the cause of the illness is unknown. This is a better and more appropriate name.

During the last couple of years several scientists have adopted IEI or a similar name: idiopathic environmental illness (IEI). This is the most neutral name to date, which, however, can lead to confusion with other environmental illnesses (Sparks, 2000). MCS is used in this report because it is still the name most commonly used in the literature.

2.3 Delimitation in relation to other syndromes and illnesses

MCS is grouped among the so-called environmental illnesses. These include several syndromes presumably caused by stress factors in the environment, but which are not officially recognized as diseases. The term MCS is often used for different environmental illnesses. See the list of environmental illnesses in table 2.4.

Table 2.4 List of environmental illnesses somewhat similar to MCS

Many people complain of the same symptoms as in MCS, while the physicians cannot detect objective signs of illness. Unlike MCS, the other environmental illnesses are not caused by exposure to chemicals but possibly by other mechanisms.

MCS is distinguished from the other illnesses by the criteria defining MCS (see subsection 2.2.2). People fulfilling the criteria defining MCS must be considered as MCS patients, even if they also fulfil criteria defining other syndromes. A number of investigations show that some people fulfil the criteria defining several syndromes. Many people with SBS or GWS (see table 2.4) also fulfil the criteria defining MCS (see chapter 4).

The most important environmental illnesses, which can be distinguished from MCS, are described briefly below.

2.4 Comments

MCS is a syndrome with subjective non-specific symptoms, unclear underlying mechanisms, and many different names. MCS belongs to the so-called environmental illnesses, among which are other poorly defined syndromes with unknown causes and with symptoms resembling those of MCS. It is easy to get them mixed up or to take one for the other.

This report focuses entirely on MCS.

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Version 1.0 March 2005, © Danish Environmental Protection Agency