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The Reality of Multiple Chemical Sensitivities (MCS)

Chemical sensitivities are negative reactions to a broad array of environmental agents. Some people report the development of allergic or asthmatic reactions when exposed to low levels of chemicals in their home or at work. Toxic chemicals in pesticides, asbestos, new carpets, and paint, etc. can cause illnesses to develop in certain people.1-3

Multiple chemical sensitivities (MCS)

MCS is also known as idiopathic environmental intolerance or environmental illness. Often reported as a medical problem, it is a physiological reaction triggered by exposures to chemicals, electromagnetic forces, or other environmental factors.

There is science to support that significant exposure to certain chemicals can make people sick and worsen conditions like asthma. However, it is not clear how low levels of exposure affect some people and not others.2

A real clinical diagnosis?

MCS is not a universally accepted medical condition. Some physicians and medical organizations believe that people with multiple chemical sensitivities report symptoms that cannot be reproduced in clinical studies.2

Others, including the American Medical Association (AMA) and the American Academy of Allergy and Immunology, do not consider MCS to be a medical problem. There is support for the belief that underlying illness contributing to multiple chemical sensitivities is psychological, not medical, meaning physical symptoms of mental conditions rather than primary medical illness.2,4

The medical community is still discussing whether multiple chemical sensitivities should be classified and diagnosed as a medical illness.4 This is because many people reporting such illnesses are exposed to common chemicals at concentrations well tolerated by most of the population.1 However, it is recognized that infectious microorganisms, allergens, and toxins can cause respiratory diseases like asthma and rhinitis which result in identifiable changes of bronchial or nasal function.2


Some chemicals are known to cause disease in humans.4 Triggers vary and include:

Common symptoms of multiple chemical sensitivities

Some chemicals, both synthetic and natural substances, can cause reactions that are similar to symptoms of allergies. They can be found in carpets, plastics, perfumes, paint, and smoke.

Reactions to medications and preservative chemicals are common in multiple chemical sensitivities, as are dysautonomia symptoms, issues associated with autonomic nervous system (ANS) that make it hard to regulate your body temperature. Joint pain, food intolerance, and airway dysfunction syndrome are common in asthma and to those with MCS. There are no specific set of symptoms associated with any particular exposure, but common symptoms include:2,4

  • Headaches
  • Nausea, bloating and diarrhea
  • Rashes
  • Asthma and other breathing difficulties
  • Muscle and joint pain
  • Fatigue
  • Memory loss
  • Confusion and mood change

Risk factors for multiple chemical sensitivities

Multiple chemical sensitivities more often appear in people with preexisting individual or family histories of migraine or allergies.1 There are no consistent diagnostic processes or lab tests that can identify the cause or existence of any medical illness in the presence of low-level exposures.2

Anxiety and other psychiatric problems, or the predisposition to anxiety disorders are present in most people who present with MCS. Although psychiatric illness does not reduce the pain and suffering, remember that mental conditions are brain disorders.2

The use of antidepressants, anti-anxiety, and sleep medications are often prescribed to treat specific symptoms. Unlike classic asthma and allergic conditions, the immune system is not involved, and immunologic tests are not indicators of MCS.2

Multiple studies report that people with MCS generally have measurably poorer social functioning compared to study controls.2

What to do about it

The medical community recommends caution to people who seek out unproven and potentially harmful treatments. Tests can be expensive, have their own risks, and not lead to any improvement.2,3 It can be beneficial to minimize exposure to triggers by modifying certain aspects of lives.2

Some people find it necessary to repair or move out of their house, change jobs, change cities, and change their diet. Physicians caution about extreme actions like these. They recommend strong social support relationships, limiting extreme actions of avoidance, and maintaining normal work, social, and family life.2,3

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. Ross GH. Clinical characteristics of chemical sensitivity: an illustrative case history of asthma and MCS. Environ Health Perspect. 1997;105 Suppl 2(Suppl 2):437–441. doi:10.1289/ehp.97105s2437
  2. Black DW. Temple S. Idiopathic environmental intolerance (multiple chemical sensitivity). Up To Date. Accessed 9/25/19.
  3. Magill MK. Suruda A. Multiple Chemical Sensitivity Syndrome. Am FamPhysician. 1998 Sep 1;58(3):721-728.
  4. Multiple Chemical Sensitivity. Johns Hopkins Medicine. Available at: Accessed 9/25/19.