Allergies: 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. The exposure may occur as a major event, such as a chemical spill, or 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."

Is MCS a Real Disorder?

Many recognized medical groups and societies, including the CDC, the American Medical Association and the American Academy of Allergy, Asthma and Immunology, do not consider MCS a distinct physical disorder. There are several reasons for this.

First, there is a lack of clinical 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, people 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% 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?

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 healthcare 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%-10% 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.

What Causes MCS?

The cause of MCS is unknown. One theory suggests that chemicals traveling 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 behavior, and memory, which may make a person more sensitive to a chemical odor previously encountered, a condition called cacosmia. However, this theory has not been proven.