What is Multiple Chemical Sensitivity?

One year ago I wrote an essay entitled ¿Qué es la SQM? (What is MCS?) by request of the Spanish CFS Investigation Forum, a prestigious forum about CFS, MCS, Fibromyalgia and related illnesses in Spanish. They have this article posted on their welcome page with another article entitled “What is CFS?”. Last summer I translated the essay into English and now it has been published at The Canary Report and Environmental Medicine Matters. The article has also been translated into German and published at CSN Blog.


What is Multiple Chemical Sensitivity?

Multiple Chemical Sensitivity (MCS) is an acquired chronic illness, not a psychological one, which manifests itself with multisystemic symptoms as a reaction to a very small exposure to chemical products, normal everyday chemicals but unnecessary ones, like perfumes, air fresheners or laundry softeners.

The symptoms, which are chronic and they become acute in a crisis, include fatigue and respiratory, digestive, cardiovascular, dermatological and neurological problems.

MCS is a syndrome with four grades of severity, so not all of us who are sick suffer the same level of disability and isolation.

It is important to note that MCS is not an allergy.

It is an illness which has been known since the 1950s, but it has yet to be recognized by the World Health Organization (WHO), despite that there are more than 100 research articles that support the organic basis of MCS, that the number of people affected is increasing rapidly, at a younger age, and that the European Parliament includes MCS in the growing number of illnesses related to environmental factors. MCS has already recognized as a physical disease in Germany, Austria, Japan and Spain.

What percentage of the population has MCS?

There are no studies in Spain, but it is thought to be affected between 0.5% and 12% of the general population, according to the grade.

In countries where there are statistics about this illness, we see that the amount of people that have MCS is not small. According to the Environmental Health Association of Quebec, 2.4% of Canadians have MCS. According to Professor Martin L. Pall, PhD, the prevalence of severe MCS in the U.S is approximately 3.5% of the population.

So MCS is not a “rare disease,” which are the ones that affect less than 0.05% of the population. MCS is an emerging and hidden disease.

Chemical products are toxic and they affect us all. Chemical products are linked to illness like cancer, asthma, allergies, autoimmune diseases or any other illness of environmental origin.

How can you know that you are developing MCS?

The most common symptom is to notice unbearable chemicals which one did not notice before. One stops tolerating various chemical agents like cleaning products, perfumes, tobacco smoke, car emissions, air fresheners, etc.

You also may stop tolerating alcohol, dairy products or gluten. You also develop intolerance to various foods and medications.

Often there are other environmental intolerances: to heat, to cold, to noise, to vibrations, to sunlight and to electromagnetic fields (computers, high power lines, telephones, cellular phone antennas, microwaves, etc).

MCS entails the loss of tolerance of chemical products in susceptible persons and there are two ways of developing MCS: from one single exposure to toxics at a high dose (fumigation, for example) or by many exposures to small amounts over the years. In the second group there are an increasing number of people with CFS/ME and FMS who, with the years, also develop MCS.

How is MCS diagnosed?

The diagnosis is clinical, based on the symptoms. There are no tests to diagnose MCS and other medical conditions must first be ruled out.

For the diagnosis, doctors use the questionnaire QEESI (Quick Environmental Exposure and Sensitivity Inventory) which is a sensitive and fast questionnaire instrument with five scales used to evaluate a person’s level of chemical sensitivity or intolerance.

6 consensus criteria for the definition of MCS:
  1. A chronic condition.
  2. Symptoms recur reproducibly.
  3. Symptoms recur in response to low levels of chemical exposure.
  4. Symptoms occur when exposed to multiple unrelated chemicals.
  5. Symptoms improve or resolve when trigger chemicals are removed.
  6. Multiple organ systems are affected.
When you have MCS and you are exposed to certain toxic chemical agents, a series of symptoms are initiated automatically like choking, irritation of the respiratory tract, tachycardia, headaches, mental confusion, dizziness, nausea, diarrhea, extreme fatigue and/or pain. These symptoms don’t get better until you stop being in contact with the chemical agent that produced it. The symptoms can last days or even weeks.

How is MCS treated?

Because of the pathophysiological bases of this syndrome are still unknown, there is no specific treatment for MCS. But there are a lot of treatments that help to control MCS and improve our health (sauna, supplements, homeopathy, etc.), and it’s very important to find a specialized doctor who studies our case, because each patient is different, depending on the genetic, the associated pathologies and the MCS grade.

Besides the treatment, is very important to put into practice the Environmental Control. Environmental Control is to basically avoid, as much as possible, any exposure to toxics or chemical substances. But in spite of this, MCS is chronic and persistent and it can reduce the quality of life of the sufferers.

Environmental Control is to avoid the chemicals or foods that may trigger reactions, avoid humid environments and avoid environments that could cause irritation (smoke, gas).  This requires that we substitute all beauty and cleaning products with ecological ones without aroma; eat organic and non-processed foods (eliminate those we don’t tolerate) cooked using non-toxic cookware; filter the drinking water and also the water for cooking and showering; use a carbon-filter mask in situations in which there are a high concentration of toxics; get an air purifier; use ecological clothing with organic fabrics and organic dyes; avoid or minimize exposure to electromagnetic fields and in general remove everything that that we don’t tolerate (furniture, clothing, cosmetics, etc.).  Sometimes is even necessary to change our residence. The Environmental Control benefits the MCS sufferer and also his entire family and it’s recommended for people with allergies or asthma in other countries. It’s also recommended for people with Chronic Fatigue Syndrome and Fibromyalgia.

Scientific evidence

In September 2008, was published the study “Is multiple chemical sensitivity a learned response? A critical evaluation of provocation studies” by Goudsmit and Howes at Journal of Nutritional & Environmental Medicine, which concluded that MCS is related to chemicals and it’s not a psychological illness.

In May 2009, Professor Anne C. Steinemann and Amy L. Davis of the University of Washington published a compilation of research on MCS with more than 100 peer-reviewed journal articles that support a physiological basis for MCS.

After that compilation, 2 important studies have been published:

In October 2009, the Journal of the Neurological Sciences published the study “Brain dysfunction in multiple chemical sensitivity” done by the Department Of Pulmonology of the Hospital Vall Hebron of Barcelona (Spain).

And at the end of April 2010 has been published the study “Biological definition of multiple chemical sensitivity from redox state and cytokine profiling and not from polymorphisms of xenobiotic-metabolizing enzymes” done by the IDI Institute of Rome (Italy) at the Toxicology and Applied Pharmacology – Elsevier.

Also last year, General and Applied Toxicology, 3rd Edition, published a chapter on MCS done by Researcher Martin Pall, PhD entitled “Multiple Chemical Sensitivity: Toxicological Questions and Mechanisms.”


Eva Caballé is an economist from Barcelona, Spain, author of the book Desaparecida: Una vida rota por la Sensibilidad Química Múltiple (Missing: A life broken by Multiple Chemical Sensitivity) published in Spanish by El Viejo Topo, Barcelona, Spain, 2009. She authors NO FUN, a Spanish blog with an English section about Green Living, MCS, and Allergies, with tips for a healthier life free of toxics. She has been a contributor at The Canary Report and at the art magazine Delirio (Delirium).