(Miller et al., 1992; Owen et al., 1990); and removing carpets (although Rose and colleagues  have shown that the use of acaricides or tannic acid treatment can also reduce mite allergen). Other control strategies for the bedroom are designed to eliminate sites in which mites can grow and to reduce dust collectors to make cleaning easier. The recent report from NHLBI (1991) is an excellent source of information regarding allergen avoidance. (See also Box 8-1 in Chapter 8.)
Three different approaches are possible for control of mite growth in the rest of the house:
Design the house with polished floors and wooden, vinyl, or leather furniture to eliminate sites where mites can grow.
Maintain indoor relative humidity at below 50 percent (absolute humidity below 6 g/kg). Korsgaard (1983a) has shown that in some areas of the world this can be accomplished by simply increasing ventilation. In other areas, it would be necessary to use air conditioning during the humid months.
Use acaricides to treat carpets or furniture, including pyrethroids (D. Charpin et al., 1990b), natamycin (an antifungal), pirimiphos methyl (Mitchell et al., 1985), and benzyl benzoate (Bischoff et al., 1990). In each case the chemicals are effective in killing the mites, although methods for applying the agents may present problems (de Saint-Georges-Gridelet et al., 1988; Platts-Mills et al., 1992).
Several different chemical treatments (as in approach 3 above) have been shown to achieve 90 percent reduction in allergen levels for a month or more. In addition, 1 or 3 percent solutions of tannic acid have been recommended for denaturing mite allergens (Green et al., 1989). Again, this method achieves a 90 percent reduction of mite allergen, but because tannic acid does not kill mites, the effect is temporary (i.e., approximately 6 weeks to 2 months). Carpets fitted onto unventilated floors—for example, in basements or on the ground floor of a house built on a concrete slab—are particularly difficult to treat. Under these circumstances water can accumulate either because of condensation onto the cold surface of the concrete or because of leakage (either domestic or rainwater from outside). In either case, once the carpet is wet, it will stay wet and become an excellent environment for the growth of fungi and mites.
For most other allergens, only case reports are available as guidance regarding the clinical effectiveness of avoidance measures. Removal is certainly the logical approach to management for most domestic animals or rodents (Wood et al., 1989); if sensitivity to insects (cockroach or others) is