:::I have no problem if this is rephrased or moved out of the lead, but Barrett and this blistering Staudenmeyer review are not being cited for their research authority—they're being cited as examples of argument. That's why the only citation to Barrett (a controversial source) is following a sentence that begins "Critics of clinical ecology . . . charge that:" Such arguments are important because they've won over a majority of doctors and courts, even if they are demagogic. I think its important to concisely introduce perhaps the primary controversy about the subject: whether or not MCS is an organic and physiological disease. 
Incidentally, a free amino acid is claimed to cause MCS.  Luke