Multiple-chemical sensitivity (MCS)



MCS is a chronic non psychological syndrome that manifests with multisystemic symptoms as a response to a minimal exposure to chemical products of regular use such as bleach, air fresheners, perfumes, etc. and that improves when avoiding such exposure.

The European Parliament defines MCS within the increasing number of diseases related to environmental factors.

Suffering from MCS means loss of tolerance to chemical exposure in susceptible people and can develop either due to a high dose of a single toxic exposition or to repeated exposure at lower doses. Within the second group there are an increasing number of people who after several years with Fibromyalgia or Chronic Fatigue Syndrome/ME develop MCS.

MCS is a syndrome manifested in 3 degrees of severity that mark the exposure limitation level and the patient's isolation.

MCS patients frequently present comorbidities such as Chronic Fatigue Syndrome, Fibromyalgia, multiple endocrine dysfunction, irritable colon, mucous dryness syndrome and irritant cystitis which aggravates the characteristic symptoms of sensitivity.

The prevalence of this syndrome in industrialized countries, according to data provided by several authors, would affect between a 2% to a 10% of the population while, according to other authors, the real number would not reach the 2%. In fact, thus, there is not enough data to reach a conclusion on this aspect.



Symptoms may begin all of a sudden or gradually, being caused by exposure to low doses of chemical agents or radiations that had been previously well tolerated. For instance, in the initial stages of the disease, a lot of smells are perceived, for the first time, as unpleasant or unbearable. Some patients develop intolerance to alcohol, dairy products or foods containing gluten or allergy to some cosmetics since they can cause skin irritation.

Once MCS has developed, there are skin, respiratory, neuropsychological and digestive manifestations, frequently chronic and persistent, which worsen during a crisis.

During a crisis caused by exposure to some toxic agent, the main symptoms are breathlessness, irritant symptoms of the skin, mucous and respiratory tract, migraine, mental confusion, nausea, diahrrea, severe fatigue, widespread osteomuscular pain and a general discomfort, preventing the person affected from remaining in such environment. As contact with the agent that caused the crisis is avoided, improvement is progressively felt within minutes, hours or after few days.

MCS is frequently accompanied by other environmental intolerances such as:

  • Solar exposure
  • Electric waves (electricity supplies, electrical household appliances, etc)
  • Magnetic waves (microwaves, telephony, electromagnets, etc)
  • Sound waves (intense or persistent noise)



MCS diagnosis is clinical, that is, based on a series of symptoms reported by patients; there aren't any analytical tests or specific explorations allowing the confirmation of the diagnosis but explorations must be done to exclude other illnesses.

The QEESI test is used in order to make a diagnosis. This test measures environmental and non-environmental intolerances and veiled exposures quantifying their severity and the repercussions on daily life.

MCS is a chronic disorder whose symptoms manifest when repeating the exposure to the agent; symptoms manifest at low concentration exposure; sensitivity manifestations improve or disappear when exposure is avoided; the same response is obtained when exposing to diverse products which do not have a relationship between them and, finally, symptoms affect several organism systems.



MCS implies a radical change in life style since chemical products, nowadays to be found everywhere, such as air-fresheners, disinfectants, perfumes, cloth softeners, etc., can no longer be tolerated.

It implies social isolation (people visiting a sick person cannot use chemical products), economic problems (high expenses to adapt to the disorder without any type of economic support), disability to work (when the grade of MCS is severe), loss of leisure (difficulty to read or watch films, phonofobia -which prevents listening to music-, etc.), home isolation (in severe cases patients only go out to visit doctors and always wearing a mask to avoid constant crisis) and also serious problems regarding medical attention since hospitals lack protocols for MCS.



MCS has no cure and there is no specific treatment since the physiopathologic basis of this syndrome is not known with exactitude.

Today, the treatment consists in environmental control but, in spite of it, the clinical symptoms can be chronic and persistent reducing the patients' quality of life.

Environmental control consists in avoiding products to which the patient is hypersensitive, avoiding damp environments, avoiding exposure to irritating agents (gases, smoke), changing conventional cleaning and hygiene products for ecologic ones, eating ecologic food (eliminating the ones we do not tolerate), drink filtered water, use activated carbon masks, air purifiers, get rid of anything in the household that causes symptomatology (furniture, clothing, cosmetics). Some times it is necessary to move houses.

Thyroids must be controlled once a year and vitamins and minerals' levels must be checked since, very often, intolerance to some food may imply an unbalanced diet with its consequent deficits.



Depending on the grade of the illness, it can be more or less disabling. It frequently requires a change in the work environment and, in the most severe cases, it may result in incapacity for work.

MCS is not yet officially recognized in our country. Clinical research and scientific meetings have been initiated in order to define by consensus some conceptual basis of the illness (i.e. "Primera reunión nacional sobre SQM" or "First national meeting on MCS"; Hospital Clínic of Barcelona, clinical toxicology section, and AETOX. October, 2009).

Sources: Sensibilidad química y ambiental múltiple. J. Fernandez-Solà y S. Nogué Xarau. JANO. Sep 2007
The Medical Perspective on Environmental Sensitivities. Margaret E. Sears. Medical Issues. May 2007
Multiple Chemical Sensitivity. Martin Silberschmidt. Danish Ministry of the Environment. 2005


More information about multiple chemical sensitivity:

Canal Salut








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