• I composed the following to indicate my thinking about MCS.

• Because doctors cannot agree on how to diagnose a disease, this does not mean that a disease does not exist. Both headaches and MCS fall into this category, as well as other diseases, if we were to think about it.
• Consider a headache as an example of a disease similar to MCS.
  • A headache is a disease
  • Nobody has seen a headache, yet we all agree that a headache can exist
  • The headache disease is diagnosed by symptoms, not objective signs
    • The pain of a headache cannot be objectively measured.
  • We agree there are headaches because many people, including maybe ourselves, say that headaches exist
    • There are some people who never get headaches, but they would agree that headaches exist
    • There are some people who only get small headaches, yet they would agree that it is logical that if small headaches exist, probably larger headaches exist too
  • It would be ridiculous and unscientific to say that headaches do not exist, even if they only severely affected a small number of people
    • The absence of "acceptable" proof is not the proof of absence
• Suppose you could demonstrate that a disease (headache or MCS) affects some people.
  • There is also some research about the prevalence of symptoms associated with MCS.
    • There are many people who do not carry the diagnosis of MCS but who are chemically sensitive
    • And, there are thousands of people who complain of this illness.
• Cause of headaches or MCS
  • Headaches undoubtably exists, even if we do not know the cause or mechanism of headaches
• Rationale for MCS
  • The analogy of allergy
    • Allergy was only identified as a disease entity in recent times, although it undoubtably existed before it was objectively diagnosed
  • Hypersensitivity is a recognized medical term
  • Recent, extended and accepted research of immune over-reactivity, presented at a recent conference that I attended, described part of the what could be the mechanism of MCS. The over-reactivity of the immune system causes more damage than the initial chemical insult.
  • Explanations that we all vary in our sensitivity to chemicals, based upon our constitution and capacity of our organs to detoxify exogenous or endogenous chemicals which could cause damage (toxic chemicals)
  • If a chemical can be deleterious to a person, and possibly cause brain injury (the brain itself has no pain receptors), it is logical that nature would provide a mechanism to alert the person of danger (symptoms) so that the person could avoid further injury (brain damage is cumulative).
    • People with MCS improve when they avoid chemical exposure. They become symptomatic with chemical exposure.
• Note new research by Dr. Davidson showing MCS in relatively naive workers exposed to gasoline (Arch Environmental Health 53(3): 183-189 (1998).