demonstrated, eradication, or moving, is the logical approach in such circumstances. At present, there is little evidence about the effectiveness of eradication measures in reducing insect allergen levels. The recent development of assays for cockroach allergens, however, means that it is now possible to evaluate avoidance measures.

The situation is much more confusing for indoor fungi. No simple assays exist for indoor fungal allergens, and the relationship between spore counts and allergen exposure is not clear. Many spores are not viable, and some allergens may only be expressed once the spore germinates (Arruda et al., 1990; Lehrer et al., 1986). It will be difficult to evaluate proposed procedures to reduce exposure to fungal allergens until accurate assays are available. Even then, evaluation of exposure will not be as simple as for mite or cat allergens. (See Chapter 6 for a discussion of monitoring for indoor fungal allergens.) It is often difficult to tell whether fungal spores come from inside or outside the house, because many species can grow in either environment. Nonetheless, it is reasonable to recommend controlling humidity, removing sites for fungal growth, avoiding basements, and cleaning surfaces with fungicides.

Grass pollen can become a major component of house dust and has been found at high levels in dust from the houses of grass pollen-sensitive patients who present for treatment with asthma (Pollart et al., 1988). Filtering incoming air or keeping doors and windows closed can help control the entry of pollens, although other problems may be created (see Chapter 7).

Conclusions and Recommendations

With most Americans spending the great majority of their time indoors—and most of that in their own houses—it is not surprising that the bulk of inhaled foreign protein is associated with indoor air. The evidence shows that a large proportion of asthmatics are allergic to indoor allergens and that several changes in the way we live indoors may have affected the levels of these allergens. These changes include increased mean temperatures, reduced ventilation (with consequent increased humidity), fitted carpets, and cool-wash detergents which have led to water temperatures for washing bedding that do not kill mites.

Once identified, reducing exposure to allergenic "trigger factors" has been a standard part of the treatment of allergic disease for many years. Since approximately half of existing cases of asthma have been attributed to allergenic factors, it is reasonable to expect that asthmatics who require more than occasional treatment might also have allergies that induce their asthma.

Recommendation: Provide appropriate allergy evaluation of asthmatics who require more than occasional treatment. Where allergic

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