You've been shown the research, Ilena.  The belief that one has been
exposed, not actual exposure, is what triggers the symptoms.
Repeated clinical trials have shown this.  Why does that bother you?

http://en.wikipedia.org/wiki/Multiple_chemical_sensitivity#Psychological_causes

Psychological causes
Several mechanisms for psychological etiology have been proposed
including theories based on stress, Pavlovian conditioning, or
misdiagnoses of an underlying mental illness. Behavior exhibited by
MCS sufferers may reflect broader sociological fears about industrial
pollution.[26]

It's difficult to differentiate psychological and physiological
etiologies of MCS because substances used to test for sensitivity can
often be detected by scent. Odor cues make double blind studies of MCS
patients difficult, and scents might provoke a psychosomatic response.
Research by Dr Mariko Saito et al from the Department of Psychosomatic
Medicine at the University of Tokyo in 2005 found that patients only
experienced symptoms when they themselves initiated the challenge
tests. When they were given random prompts, there was no difference
between MCS patients and controls in terms of physical and psychologic
symptoms.[27] Their conclusion was "MCS patients do not have either
somatic or psychologic symptoms under chemical-free conditions, and
symptoms may be provoked only when exposed to chemicals," although
their results showed that it was not the chemicals themselves that
caused the symptoms.

A review of 37 provocation studies concluded that "persons with MCS do
react to chemical challenges; however, these responses occur when they
can discern differences between active and sham substances, suggesting
that the mechanism of action is not specific to the chemical itself
and might be related to expectations and prior beliefs".[28] Critics
of such provocation studies assert that they are inconclusive because
they often employ masking odors which themselves are alleged to
trigger MCS. At least one study attempted to correct for this problem
by only using patients who do not respond to the masking odor, and
this provocation study similarly showed no correlation between
symptoms and chemical exposure.[29]

Another study found strong evidence of a placebo effect: purported MCS

sufferers claimed symptoms in nonblinded tests when fed suspected food
extracts, but were unable to produce symptoms consistently when the
tests were doubleblinded; similarly, patients responded identically to
"treatments" and saline.[30]

Science rejects mind-body dualism, so the distinction between
physiological and psychological causes is difficult to test.[28

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Wikipedia Founder Discourages Academic Use of His Creation
What kind of idiot cites Wikipedia? The point of citation is to hold an
individual responsible, or to give credit to an individual. The nature of
Wikipedia is collaborative, and thus non-static and in constant flux. There
is simply no credit to give, and thus no accountability for the truth of the
arguments. I appreciate Wales suggestions - it is quite good (I use it all
the time) for broad overviews of unfamiliar topics. It has its place, but an
academic source it is not.

Don't you have a Mathematics degree??
Exactly what is your personal experience with MCS patients?

Anyone can post studies---how does anyone know if they real
or made up?

According to Rootdown, if you aren't playing on Rootdown, you are
with your patients.

Then what are you doing about subjects--shouldn't you either be on
Rootdown or with your patients....

If not, you'd better edit your Rootdown pages, otherwise you are
lying!