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A sensitive question

Is multiple chemical sensitivity -- extreme reactions to common compounds -- a disorder, as some doctors think, or just fiction, as others say?

May 05, 2003|Valerie Ulene | Special to The Times

Few people find the smell of heavy perfume or the fumes from car exhaust pleasurable, but most can live with them. For some, however, exposure to these types of things pose insurmountable problems. They're so irritated by car exhaust, they find it impossible to go outside, or so sensitive to even small amounts of perfume, they can't go to work.

Although these scenarios may sound farfetched, a growing number of people report such extreme sensitivities to chemicals. The problem has become so common, it has even been given a name: multiple chemical sensitivity, or MCS. In a 1999 survey of California residents, nearly 16% of respondents said they were "allergic or unusually sensitive to everyday chemicals"; more than 6% had been diagnosed by a physician as having multiple chemical sensitivity.

People with this problem react to chemicals found in a variety of common products -- anything from air freshener to pesticides. "Their symptoms can run the gamut from nasal congestion to nausea, irritability, fatigue, memory problems and depression, and can range in severity from mild to incapacitating," says Dr. Fred Fung, a medical toxicologist at UC San Diego. Even very small amounts of a chemical are typically sufficient to trigger their complaints.

Some physicians believe that MCS is a unique medical disorder. The most extreme members of this group call themselves "clinical ecologists" and specialize in this type of problem. They use a variety of unproved (and, in some cases, unconventional) therapies, such as strict elimination diets, nutritional supplements and even "detoxification" regimens.

But other physicians -- at least for now -- do not classify MCS as a true disease. This group includes several major medical organizations, including the American College of Occupational and Environmental Medicine, the American Academy of Allergy, Asthma and Immunology and the California Medical Assn. Many of these doctors acknowledge that the patients could be experiencing symptoms but are not convinced that they are caused by a real medical problem. (Some doctors go so far as to say the complaints are completely fictitious.)

Unlike diabetes (which can be confirmed with a blood-sugar test) or coronary heart disease (which can be proved with an angiogram), there are no tests to identify people with MCS, because it leaves no objective evidence of its presence. For example, in spite of claims that MCS is caused by an overwhelming allergic reaction to modern day chemicals, no consistent abnormalities have been found when these patients are tested for allergic diseases.

Also, the symptoms in these patients are typically triggered by very low-level exposures -- quantities well below the level generally considered to be dangerous. Our current understanding of chemicals suggests that they just don't work this way.

The truth about MCS probably lies somewhere in between these two opinions. It's possible that some people are more likely to react to chemicals or have a heightened awareness of their presence. "That's not to say that they are actually allergic to or poisoned by them," Fung says. "They simply respond to these types of exposures more than most people."

It's also possible that some individuals may "learn" subconsciously to respond to chemicals. For example, after an initial exposure to a strong smelling chemical that causes discomfort or a real physical reaction, subsequent exposures to much lower levels of the same chemical trigger a similar, "learned" response.

However, it's unlikely that all of the symptoms these patients experience are the result of chemical exposure. In many cases, some (if not all) of their symptoms may be the result of an emotional or physical problem (such as lupus) unrelated to chemicals. Lupus (an autoimmune disease), for example, can cause a myriad of seemingly unrelated symptoms ranging from joint and muscle pain to headache, fatigue and depression. Unfortunately, this possibility is often overlooked once a patient has been labeled with MCS, and important diagnoses can sometimes be missed.

Fung puts it this way: "Doctors need to listen to their patients and be brave enough to work through all the possibilities. Sometimes the hardest thing to say to a patient is 'You don't have MCS, but here is what I can do for you to alleviate your symptoms.' "

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