Hesperian Health Guides

Multiple Chemical Sensitivity (MCS)

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HealthWiki > A Community Guide to Environmental Health > Chapter 16: Harm from Toxic Chemicals > Multiple Chemical Sensitivity (MCS)

For some people, the combined effects of many chemicals or a large exposure to even 1 chemical may cause an illness called multiple chemical sensitivity (MCS) or environmental illness. People with MCS have strong reactions to common toxins in paint, perfume, cars, and building materials.

Signs of MCS may include runny nose, itchy eyes, headache, scratchy throat, ear ache, scalp pain, mental confusion or sleepiness, fast heartbeat, upset stomach, nausea, abdominal cramping, diarrhea, and aching joints.

Because people show different signs of MCS, many health workers do not believe it is a real illness caused by chemicals. Instead, they think it is caused by emotional distress. MCS is also often mistaken for common allergies, but it is different from allergies for these reasons:

  • Signs appear each time the person is exposed to chemicals.
  • The effects are long lasting (chronic) and not seasonal.
  • Signs appear with less and less exposure.
  • The signs go away when the triggering chemicals are removed.
  • Signs appear in the presence of different and unrelated substances (such as paint and perfume, or plastics and cigarette smoke).
Prevention and treatment

The best way to prevent MCS is to stay away from chemicals that may cause it. Because each person reacts differently, treating MCS depends on the person who has it, although all improve when the toxins are removed from their environment.