Multiple Chemical Sensitivity (MCS) / Idiopathic Environmental Intolerance (IEI)

Idiopathic environmental intolerance (IEI), formerly known as multiple chemical sensitivity (MCS), is the term used to describe a condition where people report a range of recurrent nonspecific physical and psychological symptoms and attribute them to exposure to low levels of a wide range of chemical, biological or physical agents in the everyday environment. The causes of MCS/IEI are unknown.

See below for frequently asked questions: 

What triggers MCS/IEI?

Individuals with MCS/IEI identify a wide and diverse range of chemical, biological and physical factors as symptom triggers, including:

  • carpeting, soft furnishings, printing ink, soft plastics, synthetic fabrics, cleaning products
  • chlorinated and fluoridated water
  • cigarette smoke
  • electromagnetic field
  • fragranced products such as perfumes, aftershave, and deodorants
  • pesticides, pharmaceutical drugs and anaesthetics
  • volatile organic compounds, paint, solvents.

The symptoms of MCS/IEI are reportedly triggered by exposure to very low levels of perceived triggers, i.e. background levels of exposure, which do not cause concern for the vast majority of the population.

It is not known what causes the condition and how it develops. Despite extensive research over the past 50 years, there is little understanding of the causes and pathophysiological mechanisms of MCS/IEI. Several toxicological mechanisms have been proposed, but the scientific evidence is lacking.

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What are the symptoms of MCS/IEI?

The individuals reporting MCS/IEI pesent with broad range of symptoms involving different organs and systems. There is no consistency in the reported symptoms from patient to patient. Individuals with MCS/IEI commonly report headache, fatigue, confusion, depression, shortness of breath, arthralgia, myalgia, nausea, dizziness, memory problems, gastrointestinal symptoms, and various respiratory symptoms.

The symptoms of MCS/IEI are real to the person who reports them, despite the lack of medical explanation.

Some of the symptoms reported by MCS/IEI individuals may be debilitating and may take a significant toll on many aspects of their everyday life, including relationships, lifestyle, and work.

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How is MCS/IEI diagnosed?

There are no universally accepted diagnostic criteria for MCS/IEI. There are no laboratory tests and no clinical guideline documents. MCS/IEI is not recognised as a medical condition in Australia and most countries.

Individuals with MCS/IEI symptoms who seek help from their GPs are frequently referred to various specialists. If following clinical investigations there is still no explanation for the symptoms, these patients are usually provided with explanation, reassurance, and guidance on trigger avoidance measures.

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Can MCS/IEI be treated?

There are no clear evidence-based treatment options for MCS/IEI.

Individuals with MCS/IEI consider education, support and acknowledgement as the most beneficial interventions. Other effective treatments reported in the literature include psychotherapy and cognitive behavioural therapy.

Some groups promote a wide range of interventions, ranging from intravenous injections of vitamins and nutritional supplements to ‘detoxification therapies’ such as sauna, colonic irrigation and others. The efficacy of these interventions in the treatment of MCS/IEI has not been tested systematically and they are not supported by medical practitioners.

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Does trigger avoidance help?

Trigger avoidance is a common approach to the management of MCS/IEI symptoms because many individuals with MCS/IEI report feeling better when they intentionally avoid the factors they report as triggers for their symptoms.

However, there is no conclusive scientific evidence that perceived trigger avoidance is effective in treating the condition. Several controlled exposure studies showed that individuals reporting MCS/IEI tend to develop symptoms only when they are aware of being exposed to a trigger. More research is needed in this area.

It is prudent at all times to strive to maintain a healthy environment in the home and at work.

Better air quality, particularly good building ventilation, helps to maintain good health and benefits people with many medical conditions, including those who report MCS/IEI.

It is also wise to minimise the use of household chemicals, such as pesticides, disinfectants, solvents and others. Use them only when needed, and always follow the label instructions.

At work and in public settings it is important to appreciate that for some individuals, exposure to certain chemical or physical agents may result in considerable distress. Workplaces and public settings should, therefore, endeavour to take reasonable steps to accommodate the needs of people reporting MCS/IEI whenever possible.

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Further information

For further information on MCS/IEI, contact SA Health’s Scientific Services on (08) 226 7100, or visit the report A review of the Multiple Chemical Sensitivity (MCS) Guidelines for South Australian Hospitals 2010 (PDF 377KB).

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