For those of you who think that your problems would be over if you retreated indoors, you will be saddened to learn that your home may not truly be your castle. The air indoors is often filled with an array of potential allergens, including dust, mites, mold spores, animal dander, saliva, and dried food particles. If hay fever sufferers are sometimes said to have "allergic noses," then those unfortunate souls who have year-round allergies to these abundant allergens certainly merit the same description. And since the upper respiratory symptoms that are typically provoked persist throughout the year, these allergies are aptly referred to as perennial allergic rhinitis.

Dust
Dust is so abundant that most of us take it for granted that we know what it is. But to say that dust is merely floating "dirt" that settles on your furniture or clothing is only partly correct. While it can be glam-orously described as dazzling, dancing, iridescent swirls of particles seen when a beam of sunlight shines through a window, it is more complex than that; it is a mixture of many things in the home environment. It may be an accumulation of any or all of the following: outside dust, pollens, dried food particles, mold spores, insect parts and droppings, lint, synthetic fibers, hair fragments, powders, hair spray mists, animal dander, dried saliva and urine, and shed human skin cells. In genetically predisposed individuals, any or all of the many components of dust may be allergenic. (Because the issue of perennial allergies to household pets is an important and often emotionally charged one.)

The contribution to allergies by whole insects or bug fragments, such as wings, and the excrement they deposit everywhere deserves a few words by itself. It is very likely that most dust contains insect fragments to some extent, and they are believed to be the sources of troublesome allergies for many people. Insects whose remains have been commonly associated with respiratory allergies include the caddis fly, mayfly, and the elm bark beetle. The airborne parts or excreta from other insects, including the house mite (discussed below), may also trigger allergies in certain people.

But the ubiquitous cockroach appears to be especially problematic. It is estimated that millions of people are allergic to them mostly to their body parts, not the feces. In one study of one hundred asthmatics in southwest Chicago, investigators found that 60 percent of them were allergic to cockroaches or their debris and required repeated hospitalization despite the regular use of their medications.