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Diseases & Conditions

Multiple Chemical Sensitivity

What is multiple chemical sensitivity?

Multiple chemical sensitivity (MCS) is the name given by some to a condition in which various symptoms reportedly appear after a person has been exposed to any of a wide range of chemicals. As a result of their 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."

Is MCS a real disorder?

MCS is controversial. Many recognized medical groups and societies—including the Centers for Disease Control and Prevention, the American Medical Association and the American Academy of Allergy, Asthma and Immunology—do not consider MCS as a distinct physical disorder. There are several reasons for this.

First, there is a lack of clinical research evidence to support a physical cause for the symptoms. In addition, people with MCS do not develop antibodies in response to chemical exposure, as is the case with an immune system, or allergic, reaction. Further, patients with MCS also have high rates of mental health disorders, including depression, anxiety and somatoform disorders (mental disorders that are expressed through physical symptoms). About 50 percent of people with MCS meet the criteria for depression and/or anxiety disorders. Much of the controversy, then, centers on whether the symptoms associated with MCS are caused by physical or psychological factors.

What are the symptoms of MCS?

MCS may be the only ailment in existence in which the patient defines both the cause and the manifestations of his or her own condition. Virtually any symptom has been attributed to the syndrome, but the symptoms generally occur in one of three categories: central nervous system symptoms, respiratory and mucosal irritation, or gastrointestinal problems. People with MCS have reported a wide range of symptoms, including:

  • Headache
  • Fatigue
  • Dizziness
  • Nausea
  • Irritability
  • Confusion
  • Difficulty concentrating
  • Intolerance to heat or cold
  • Earache
  • Stuffy head or congestion
  • Itching
  • Sneezing
  • Sore throat
  • Memory problems
  • Breathing problems
  • Changes in heart rhythm
  • Chest pain
  • Muscle pain and/or stiffness
  • Bloating or gas
  • Diarrhea
  • Skin rash or hives
  • Mood changes

How common is MCS?

Many health care practitioners do not recognize MCS as a disorder 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 estimate suggests that 2 percent to 10 percent of people suffer some disruption in their lives because of MCS, although other experts believe these estimates are too high. The U.S. Environmental Protection Agency reported that about one-third of people working in sealed buildings claimed to be sensitive to one or more common chemicals. More women than men claim to have MCS, and it appears to occur most often in people between the ages of 30 and 50 years.

How is MCS diagnosed?

Unlike allergies or other immune-mediated sensitivities, which can be confirmed through appropriate testing, there are no tests to diagnose MCS. However, it is important for the physician evaluating a patient with suspected MCS to rule out organic pathologies that may be mistaken for MCS, if the history is indicative. These can include somatic disorders such as allergic rhinitis, occupational asthma, irritant-induced asthma, or reactive airways dysfunction syndrome. Other illnesses that can mimic MCS include those with vague or subtle presentations, such as hypercalcemia, hypothyroidism, systemic lupus erythematosus, multiple sclerosis, and fibromyalgia. Psychiatric illnesses that may coexist with MCS, present as MCS, or mimic MCS include somatoform disorders, panic and other anxiety disorders, depression, and personality disorders.

How is MCS treated?

Many health care providers recommend avoiding the chemicals or foods that seem to trigger reactions. While this advice makes logical sense, in extreme cases of MCS it can lead to social isolation and withdrawal. The best advice is to establish a respectful and empathetic physician-patient relationship. The goals of therapy should be to maximize rehabilitation, control (not cure) symptoms through education, and provide reassurance. Essential to this is the treatment of any concomitant psychiatric or somatic illness.


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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 1/15/2014…#10021