Not all unpleasant reactions to everyday substances are accompanied by a jump in IgE or other antibodies in the blood. You can develop stomach upset, a headache, heart palpitations or anxiety from drinking coffee, yet your antibodies don’t budge an inch.

Tartrazine (FD&C Yellow No.5), a widely used food coloring, produces hives or asthmatic attacks in sensitive people – with no apparent rise in antibodies. The fact that some reactions are not accompanied by measurable levels of antibodies doesn’t prevent them from being called allergies by some doctors.

There are, after all, other mechanisms in the immune response besides the antigen antibody reaction – some only recently discovered, some no doubt awaiting discovery. Some doctors believe, for instance, that chemicals and drugs that cause allergiclike reactions work directly on the basophils and mast cells with no antibody intervention whatsoever.

Out of that school of thought has evolved the concept that anything in our environment – including the food we eat, the air we breathe, the water we drink and the places where we work and play – can trigger unpleasant reactions in certain people.

That concept harks back to the original definition of allergy: any unusual adverse reaction. So this view, while revolutionary when compared to the modern understanding of allergy, at the same time makes simple, old fashioned common sense. Many doctors who espouse the new approach call themselves clinical ecologists.

Some are allergists; other are ear, nose and throat specialists, doctors of internal medicine, psychiatrists or primary care physicians. These doctors take up where traditional allergists leave off. Environmental factors have more of an impact on health and well being than has been previously acknowledged, then say.

So in addition to considering well known allergies to dust, mold, pollens, fur and a handful of foods, doctors taking this tack give special attention to individual susceptibility to factors usually overlooked by traditional allergist – patricides, herbicides, food additives and other chemicals infused into the food, water, air and homes of the twentieth century.

That in itself is the subject of considerable debate. Because reactions to environmental additives don’t always trigger a rise in immune complexes like IgE, they are not always regarded as a bona fide allergy by doctors in the mainstream of medical practice. Sensitivity, yes, agree traditional allergists. But allergy? No. And that difference of opinion as to what is and isn’t an allergy has also led to differences in the methods of treatment.