Memorandum by Professor Simon Wessely,
King's College, London
I am not an allergist, nor an immunologist.
I am an epidemiologist, interested in the distribution and causation
of illness, and a psychiatrist, interested in the social and psychological
aspects of illness. I directed a unit at King's College London
that has studied many aspects of chronic fatigue syndrome and
related unexplained illnesses such as "multiple chemical
sensitivity" (MCS) 44, and I now direct a unit that researches
many aspects of military health, including Gulf War illnesses.
I have published over 500 professional original publications on
these subjects.
We recently published a review of 37 "provocation"
studies in which MCS sufferers were exposed to various stimulants
in controlled conditions. The conclusions were 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
beliefs" (J Allergy Clin Immunol 2006: 118: 1257-1264).
This supports the strong consensus amongst clinical
and academic immunologists that the phenomenon of multiple chemical
sensitivity cannot be explained by allergy and/or immunological
mechanisms (in contrast for example to allergic reactions to single
substances such as peanuts). On the other hand, there is convincing
experimental evidence that this can be explained by psychological
conditioning, in which exposure to a stimulus such as an unpleasant
odour becomes associated with a physiological reaction. The fact
that symptoms develop only when the person is consciously aware
of the stimulus (as opposed to peanut allergy for example) and
that in double blind controlled tests these reactions cannot be
reliably reproduced, speaks strongly to a conditioning model.
Social, cultural and psychological factors related to perceptions
of risk further amplify these reactions. I am not saying, and
do not believe, that these symptoms are imaginary or "all
in the mind", but I am saying that social and psychological
factors have more explanatory power than immunological or allergic
factors.
Why does this matter? Considerable evidence
shows that many (but not all) diagnoses of MCS are in reality
misdiagnoses of other, often fairly straightforward, conditions
such as depression or anxiety. A label of MCS not only means that
such people then do not receive appropriate evidenced based successful
treatments, but may instead receive treatments that do little
good and in some cases considerable harm. I have in the last 20
years as a consultant seen a number of unwell patients who have
received a diagnosis of MCS. So far this has only come from the
private "alternative allergy" or "clinical ecology"
sector. For some this has had unintended, but serious consequences
for both health and bank balance. For me these have been some
of the most distressing experiences of my clinical career.
44 "Multiple chemical sensitivity" has
become a popular term, it would still be more appropriate to talk
about chemical intolerance rather than sensitivity. MCS is not
recognized in the WHO International Classification of Diseases.
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