Do you feel worse after smelling:

• The odor of household cleaning products and detergents such as bleach, ammonia and polishes?
• The fumes from furnace, auto or bus exhaust, tarred roads, kerosene heaters, floor wax, gasoline, coal smoke or other petroleum products?
• The fumes recently cleaned clothing, upholstery or rugs?
• The odor of lighter fluid, moth balls or insect repellent?
• The vapor from chlorinated water?
• The fragrance of soaps, shampoos or bath oils?
• Scented candles or decorations?

If you answered yes to any of those questions, you may be allergic to various chemical odors and fumes.

Some people, for instance, are allergic to the odors of trees, grass, weeds and flowers, rather than to the pollen itself. For some, the smell of pine paneling or a Christmas tree is enough to set off an attack. Other people are so allergic to fish, eggs or other foods that even the smell of those foods can make them sick.

What’s the link between odors and sensitivity?

”The nose provides a direct route to the brain for odors,” explains Iris R. Bell, M.D., Ph.D., a psychiatrist in San Francisco who has a keen interest in environmentally induced health problems. In fact, the smell receptors in the brain are located right behind the uppermost cavities of the nose. And, for people who are sensitive, when the chemical fumes reach the brain, they tend to effect thinking and behavior.

”Most toxic gases work in one way or another to reduce oxygen availability to, the tissues,” says Francis Silver, P.E., an engineer from Martinsburg, West Virginia, who specializes in the effect of gases on health. ”With oxygen deficiency, the brain and nervous system is affected first and foremost, impairing judgment and causing other behavioral problems.”

But when it comes to being affected by chemicals, even the experts can’t always tell weather a reaction is allergy or out and out poisoning. To complicated the matter, some people seem immune to a substance that makes other people sick, says Kendall Gerdes, M.D., an allergist in Denver, Colorado. ”On one end of the scale are people who could live in a chemical factory because they’d get sick. Most of us fall somewhere in between.”

So called moderate exposure is where the real trouble starts.

”Many of our modern advances expose us to substances which are not lethal in small doses,” says Dr. McGovern. ”But when you add up the amount of the chemicals you’re exposed to daily in the pesticide sprays, the formaldehyde, the photocopier, et cetera, it often approach toxic levels.

Even though these may be small amounts, they add up to enormous doses in the course of the day. Once you exceed your tolerance for these chemicals in your system, your immune system becomes impaired. And you’re stuck with allergies.”

Dr. Gerdes told us, ”The highly sensitive people are the front line as we move into a more and more polluted society. The things that bother chemically sensitive people are no different from the things that, with a grater degree of exposure, will eventually bother the majority.”

Sensitivity sometimes goes unnoticed until an individual is blasted by a single large exposure that finally triggers a breakdown in health.

”A person may have only a slight sensitivity to chlorine, for example, and one day a tank accidentally ruptures in his or her town,” says Dr. Gerdes. ”The toxic exposure may then change that moderately sensitive individual in some way so that time on, he or she can no longer tolerate chlorine – or any other chemical, either. The stress is additive.”

Doctors we spoke to agree that it's not all that important whether you label the chemical reaction ”allergic,” ”sensitive,” or ”toxicity.” The critical thing is to find out what bothers you and to do something about it.