Multiple Chemical Sensitivity

I have long been skeptical of the diagnosis of multiple chemical sensitivity (MCS). Here’s what I wrote about it four years ago in an article in Skeptic magazine:

An episode of ABC’s Nightline news show about Dr. Rea’s controversial diagnoses and treatments aired in 2009. I was appalled by the interviews with a patient diagnosed by Dr. Rea as sensitive to almost everything in her environment. She can’t work or leave home; her whole life revolves around her treatments. She moved to an island and created a pollutant free home. She won’t use her telephone because the magnets in it give her headaches. She spends two hours a day inhaling oxygen. She injects herself daily with a variety of unconventional “allergy” shots, including mercury! Curiously, she has no sensitivities to her dogs, her horses, or the dust kicked up as she rides in a dirt arena. Nightline also interviewed a real allergy specialist who said these people are reacting to stress, have underlying psychiatric issues, and have developed a conditioned response to experience symptoms when they encounter an odor or anything else they think they are sensitive to.

My suspicions have just been validated. In the April 17 issue of Consumer Health Digest, Stephen Barrett announced that a report has been issued by Quebec’s public health agency Institut national de santé publique du Québec (INSPQ).

The report was commissioned by Quebec’s Ministry of Public Health and Social Services, which asked them to investigate the state of knowledge about MCS. They did a very thorough job, analyzing over 4,000 articles. The report consists of 823 pages and is in French, but a one-page summary and a four-page summary are provided in English.

McGill’s Jonathan Jarry’s independent review of the report calls it a textbook on MCS. He reviews the proposed underlying pathophysiologic mechanisms and the reasons they were rejected. The evidence is now clear, and the conclusion is that “trace amounts of chemicals are not to blame. … MCS is a type of anxiety disorder in which anticipation of a danger causes very real and debilitating physical symptoms.”

Patients who have been diagnosed with MCS and clinicians who have been treating it were understandably reluctant to believe these findings. Jarry’s article was criticized, and he answered his critics in another article. 

I feel vindicated. These patients are definitely sick and deserve professional help, but effective help must be grounded in reality. 

Note: Consumer Health Digest is a great resource, and it’s free. If you’re not already a subscriber, there is a convenient subscribe button at the bottom of their web page at

This article was originally published in Skeptical Inquirer.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

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