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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."

What Are the Symptoms of MCS?

The symptoms of MCS may include:

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?

Because little is understood about MCS, some health care practitioners may not recognize 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 estimate suggests that 2%-10% of people may have some disruption in their lives because of MCS. In fact, the U.S. Environmental Protection Agency reports that about one-third of people working in sealed buildings claim to be sensitive to one or more common chemicals.

Studies show that more women than men appear to have MCS, and this sensitivity occurs most often in younger adults between the ages of 30 and 50.

In addition, studies have shown that symptoms of MCS are more common among military personnel, particularly Persian Gulf War (PGW) veterans. Some findings show that PGW veterans have an increased sensitivity with behavioral 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 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. However, this theory has not been proven.

Another theory suggests that the immune system is somehow damaged in people with MCS. Yet another theory, called "toxic-induced loss of tolerance" (TILT), suggests that acute or chronic exposure to chemicals causes some susceptible people to lose their tolerance for chemicals they previously could tolerate.

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