Environmental Sensitivities or Intolerances (ES) / Multiple Chemical Sensitivity (MCS) is an acquired environment linked condition.

It’s sometimes associated with Myalgic Encephalomyelitis, Chronic Fatigue Syndrome and Fibromyalgia.


ES/MCS symptoms involve:

Having a relatively strong sense of smell

Difficulty concentrating

Feeling dull or groggy

Feeling spacey

Symptoms may also include:


Fast or irregular heart beat

Achy muscles and joints



Nausea, diarrhea or constipation

Balance and coordination problems

Burning and irritated eyes


Frequent or urgent urination

Irritability and depressed mood

Stuffy or runny nose

Characteristics of ES/MCS include:

  • Reproducible symptoms with repeated chemical exposure and to multiple chemically-unrelated substances
  • Chronic condition
  • Symptom manifestation upon low levels of exposure (lower than previously or commonly tolerated)
  • Symptom improvement or resolution when the incitants are removed
  • Symptoms involving multiple organ systems

Information is in accordance to the 1999 consensus definition on MCS (in the Archives of Environmental Health) and the report Multiple Chemical Sensitivity Discriminant Validity of Case Definitions ((in the Archives of Environmental Health–2001:56(5)406 412).

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