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What is multiple chemical sensitivity?

Multiple chemical sensitivity (MCS) is the name given by some to a condition where various symptoms reportedly appear after a person has been exposed to any of a wide range of chemicals. The exposure may occur as a major event, such as a chemical spill, or coming into contact with pesticides used for crop spraying if you live in a rural area. It can also come from long-term contact with low levels of chemicals, such as in an office with poor ventilation. As a result of exposure, people with MCS develop sensitivity and have reactions to the chemicals even at levels most people can tolerate.

Other names for this condition are "environmental illness" and "sick building syndrome".

What are the symptoms of MCS?

People with MCS have reported a wide range of symptoms, including:

How common is MCS?

Because little is understood about MCS, some doctors may not recognise MCS as a medical illness and, therefore, do not make a diagnosis of MCS. For this reason, it is not possible to assess how many people actually suffer from MCS. One US estimate suggests that 2-10% of people may have some disruption in their lives because of MCS. In addition, studies have shown that symptoms of MCS are more common among military personnel, particularly Gulf War veterans. Some findings show that veterans have an increased sensitivity with behavioural changes to smog, vehicle exhaust, cosmetics, and chemicals.

What causes MCS?

The cause of MCS is unknown, which makes it hard to diagnose and treat. One theory suggests that chemicals travelling in the air enter the nose and affect an area of the brain called the limbic system. The limbic system plays a role in emotions, motivated behaviour, and memory, which may make a person more sensitive to a chemical odour previously encountered. However, this theory has not been proven.

People with MCS identify many products as chemical triggers, including:

  • Tobacco smoke
  • Perfume
  • Traffic exhaust or petrol fumes
  • Nail varnish remover
  • Newspaper ink
  • Hair spray
  • Paint or paint thinner
  • Insecticides
  • Artificial colours, sweeteners and preservatives in food
  • New carpet
  • Flame retardants on clothing and furniture (such as mattresses)
  • Chlorine in swimming pools

How is MCS diagnosed?

In diagnosing or treating MCS, the patient case history is very important. It needs to be very specific and detailed, and include details of daily routines and of when and where symptoms are better or worse. Checking daily, weekly or seasonal routines may help to determine cause and effect.

Sometime symptoms will have started after moving into a new house or after a particular exposure, or may show up as a result of something that the patient does on a particular day each week. The doctor may use medical tests, such as X-rays and blood tests, to rule out allergies to foods, inhalants, or chemicals and other physical or mental health disorders as the cause of the symptoms. It’s important that the doctor does not dismiss the complaints of someone with suspected MCS. In fact, a thorough medical examination is essential if MCS is suspected. Many doctors value a consultation with allergy specialists and other specialists to help make an accurate diagnosis.

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