PULLMAN, Wash.–Volatile chemicals, those that change readily to a vapor, are everywhere. They’re in new carpets and finishes on fabrics. They’re in varnish and paint, foam insulation, food preservatives, cleaning supplies and the gas stove. For people with “multiple chemical sensitivity,” these chemicals mean altered lifestyles. They may even mean giving up work and retreating into a self-made chemical-free environment.
Multiple chemical sensitivity or chemical intolerance is not a well-defined condition. The symptoms vary from patient to patient and mimic those of other diseases. Some patients attribute their problem to one exposure to a large amount of a chemical such as from a spill, while others attribute theirs to a series of exposures to small amounts such as might happen at work. The common feature all these cases share is an intolerance to one or more chemicals. The common behavior all share is an avoidance of chemicals.
While many physicians dismiss chemical intolerance as neurotic, patients insist their problems are real.
“I’ve been trying to stay on the fence with regard to the origin of chemical intolerance,” says Barbara Sorg, assistant professor in the Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology at Washington State University. She is investigating the physiological processes involved in its development.
Sorg’s expertise lies in an area called sensitization, a very general phenomenon through which the brain amplifies its response. For example, multiple exposure to stress or a drug of abuse such as cocaine causes a heightened response to the drug. Because chemical intolerance shares several features with sensitization, Sorg and others feel that the two are related.
As her working hypothesis, Sorg is exploring the premise that the same part of the central nervous system is involved in the processes that result both in chemical intolerance and in sensitization from drug abuse. Her early experiments support that hypothesis.
Experimental sensitization with cocaine involves giving an animal cocaine daily for a period of time, waiting for several days, and then testing for the heightened response that characterizes sensitization. Substituting a stress for the daily dose of cocaine also results in the heightened response, though the two processes are not exactly the same.
Sorg has taken the basic sensitization protocols and substituted the volatile chemical formaldehyde at various places. It works. Formaldehyde can replace the daily dose of cocaine or stress. The daily dose can be large or it can be small if given over a longer period on a schedule consistent with exposures to small amounts in the workplace. Furthermore, stress can sensitize an animal to formaldehyde. In other words, stress can cause animals to be more fearful of formaldehyde.
At this time, it looks as if the formaldehyde acts more like a chemical stress than a drug of abuse, says Sorg. Many who are chemically intolerant are insulted when stress of any kind is suggested to be part of their problem. But the effects of stress on the body are as real as drug effects, she notes.
Individual susceptibility to stress and drugs of abuse is undoubtedly related to an individual’s genetic makeup. “But we don’t know what makes an animal or human more susceptible to sensitization by cocaine or stress,” she says, ” therefore, we don’t have an answer for chemical exposures.”
Finding the answer will take a long time. But whatever chemical intolerance is, it is prevalent in the population. The general literature reveals an estimated 5 percent of the U.S. population is chemically intolerant, and patients average 23 health care visits per year. Eighty percent of those with Gulf War syndrome have new chemical intolerances.
The uncertainty of chemical intolerance will be further addressed next year, when Sorg plans to host a conference titled “Role of Neural Plasticity in Chemical Intolerance,” May 21-23 in Coeur d’Alene, Idaho. For 5 percent of the population, the answers can’t come any too soon.

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