The many names of Multiple Chemical Sensitivity



There used to be more than two dozen names for chemical sensitivity. Here is the story of the names.


Keywords:  multiple chemical sensitivity, chemical sensitivity, MCS, idiopathic environmental intolerance, environmental sensitivity, history.      



By the early 1990s there were about two dozen names for MCS, and more were added during the decade. They were created by various physicians, patient activists and the media.


Everybody wanted a descriptive name that conveyed a message, but there was little agreement on what that message should be. Since there was no official name for the disease, it was a jungle of names:


Multiple Chemical Sensitivity (MCS)
Environmental Illness (EI)
Chemical Sensitivity (CS)
Toxicant-Induced Loss of Tolerance (TILT)
Idiopathic Environmental Intolerance (IEI)
Petrochemical Problem
Chemically Injured
Twentieth Century Disease
Total Allergy Syndrome
Persian Gulf War Syndrome
Universal Allergy
Universal Reactor
Chemical AIDS
Chemical Hypersensitivity Syndrome
Environmental Hypersensitivity
Cerebral Allergy
Multi-organ Dysesthesia
Multiple Symptom Complex
Non-specific Hyper-responsiveness
Immune Dysfunction Syndrome
Chemically Induced Immune Dysregulation
Environmental Maladaption Syndrome
Allergy Toxemia
Clinical Ecology Syndrome
Ecological Illness
Environmental Stress Syndrome
Environmental Somatization Syndrome
Odor Aversion
Toxic Agoraphobia

Names used during the 1990s.



Sources: (Miller, 1993; IPCS, 1996; Ashford, 1998: ch 7: Randolph, 1990).


Most of these names disappeared by the year 2000. A few new ones have since surfaced:


Multiple Chemical Sensitivity (MCS)
Chemical Sensitivity (CS)
Environmental Illness (EI)
Environmental Sensitivities (ES)
Idiopathic Environmental Intolerance (IEI)
Toxicant-induced Loss of Tolerance (TILT)
Sensory Hyperreactivity (SHR)
Chemical Intolerance
Chemical Traumatic Brain Injury
Environmentally Annoyed

Names used since year 2000.



Multiple Chemical Sensitivity (MCS) was coined by Mark Cullen in his 1987 book Workers With Multiple Chemical Sensitivities, and within five to ten years it became the dominant term, which it still is today.


Environmental Illness (EI) is one of the oldest names. It is still used by some, and may now be used to include electrical sensitivity as well as MCS.


Chemical Sensitivity (CS) is sometimes used for less severe cases of MCS. The prominent MCS physician, Dr. William Rea, has multiple times expressed he preferred this term instead of MCS, with the logic that some people may be sensitized to just one chemical.


Environmental Sensitivities (ES) is a later addition to the list, sometime after year 2000. It is mostly used in Canada, and usually includes electrical hypersensitivity (EHS) as well.


Idiopathic Environmental Intolerance (IEI) was created in 1996 by a group of physicians and industry lobbyists who wanted a name that did not include the word "chemical," since that did not reflect well on the chemical industry. They also wanted a name that suggested a psychosomatic illness - "idiopathic" means "unknown," but in praxis means psychosomatic.


This was all done by a stacked panel to make it look like the new name was widely supported, especially by the World Health Organization. This sordid story is well documented (Abrams, 1996; Ashford, 1999: ch 9; EI Wellspring, 2020; IPCS, 1996).


IEI has since been strongly promoted by those who oppose the acceptance of MCS. Today it is commonly used in articles about MCS written by psychiatrists and psychologists.


Toxicant-induced Loss of Tolerance (TILT) was first used by Claudia Miller in 1997 (Miller 1997).


Petrochemical Problem was the term used by Dr. Theron Randolph who first described the illness (Randolph, 1980, 1990). In the earlier years he used the word "susceptibility" in various contexts, but not as a real identifying term (Randolph, 1962).


Some activists wanted a name that strongly conveyed the impact of MCS. The most common was Chemical Injury. The patient group Chemical Injury Information Network (CIIN) started in 1990.


Twentieth Century Disease came from the observation that MCS didn't exist before the chemical industry's products became a part of our daily lives. This began right after World War II. The name died out as the twenty-first century approached.


Persian Gulf War Syndrome (later shortened to Gulf War Syndrome or GWS) appeared a few years after the Gulf War of 1990-1991 where many service members got sick with what still seems like a version of MCS.


Universal Reactor denoted those most severely affected by MCS, who became sensitive to almost everything. It was used in some books and newspaper articles. A newsletter started in the mid-1980s by Environmental Health Network in California was called The Reactor and later The New Reactor.


The name Chemical AIDS appeared in the 1980s, when the AIDS epidemic was raging. Both diseases appeared to affect the immune system, were mysterious and ignored by the health authorities. They both could produce a great variety of symptoms, some of which were similar. Several people in San Francisco initially thought they had AIDS, before they realized it was MCS. The AIDS activists were much more effective at getting the medical community to help - eventually - than the MCS community ever was (Molloy 2019).


Some doctors at the time might have used the term as well, as they thought MCS was a sort of chemically-induced immune deficiency.


Chemical Hypersensitivity Syndrome was the term used by the California legislature when it in 1984 passed a bill (AB 3587) to provide research and public education about MCS. The bill was vetoed by Governor George Deukmejian.


Some of the names included the word "allergy," since that made it understandable to anyone. But MCS does not activate the IgE allergy mechanism and is not an allergy as now defined, so allergists were vehemently opposed to these names. The popular press kept using the word for many years, especially in headlines such as "allergic to life" or "allergic to the world."


The newest addition to the list is Environmentally Annoyed, which appeared in a 2009 article that is not at all sympathetic to people with MCS (Eek, 2009). Perversely, the article also suggests people with MCS are commonly smokers!


Many names used as ridicule

People who attacked the legitimacy of MCS sometimes used the many names as a tool to ridicule the people with the illness. An example was found in a front-page feature article in Forbes magazine (Huber 1991).


MCS has never really been known by more than a handful of names at any given time. This is similar to tuberculosis, which was once known by several names, such as consumption, scrofula, phthisis, long sickness, Potter's asthma and King's evil.



Abrams, Herbert et al. Letter to directors-general World Health Organization, International Labor Office, United Nations Environment Program, and director of International Program on Chemical Safety, April 17, 1996. (Later published in Archives of Environmental Health.)


Assembly Bill 3587, California Legislature, February 17, 1984.


Ashford, Nicholas and Claudia Miller. Chemical Exposures: Low Levels and High Stakes (second edition), New York: Van Nostrand Reinhold, 1998. Chapter 9.


Cullen, Mark R. (editor). Workers With Multiple Chemical Sensitivities, Philadelphia: Hanley & Belfus, 1987.


Eek, Frida et al. Health care utilisation and attitudes towards health care in subjects reporting environmental annoyance from electricity and chemicals, Journal of Environmental and Public Health, 2009.


Huber, Peter. Junk science in the courtroom, Forbes, July 8, 1991.


IPCS (International Program on Chemical Safety). Report of Multiple Chemical Sensitivities (MCS) Workshop, Berlin, Germany 21-23, February 1996.


Miller, Claudia. White paper: chemical sensitivity: history and phenomenology, Toxicology and Industrial Health 10, 1994.


Miller, Claudia. Toxicant-induced loss of tolerance - an emerging. theory of disease? Environmental Health Perspectives 105, 445-453 (supp2), March 1997.


Molloy, Susan. Personal communication, 2019.


Randolph, Theron. Human Ecology and Susceptibility to the Chemical Environment, Springfield, IL: Charles C. Thomas, 1962.


Randolph, Theron and Ralph Moss. An alternative approach to allergies (first edition), New York: Harper and Row, 1980. (revised edition, 1990).


More MCS history

More articles about the history of MCS available on