In the first 6 months of this previously published, randomized trial, the combined intervention of occupant education, insecticide bait application, and professional cleaning significantly reduced cockroach numbers and Bla g 1 levels in inner-city homes. This continuation study investigated whether the Bla g 1 reductions achieved by month 6 could be maintained through month 12 with insecticide application alone.

Control homes were crossed over into a cockroach extermination arm at month 6. In all homes, cockroach traps were set at months 6, 9, and 12; insecticide baits were placed as needed at months 6 and 9; and dust samples were collected at month 12.

Among intervention homes, Bla g 1 concentrations remained essentially unchanged from months 6 to 12. However, among crossed-over control homes, the geometric mean Bla g 1 concentrations (U/g dust) decreased from 287 to 14.4 for kitchens (95% reduction), from 28.8 to 5.6 for living rooms (81% reduction), from 26.7 to 4.7 for bedroom floors (82% reduction), and from 7.2 to 2.4 for beds (67% reduction). At month 12, Bla g 1 concentrations did not significantly differ between the 2 groups (P>.64 at each location). Similar results were seen for the allergen Bla g 2.

Reductions in cockroach allergen concentrations achieved through the combined intervention of occupant education, insecticide application, and professional cleaning can be maintained with continued cockroach control. Surprisingly, and in contrast to previous reports, insecticide application alone significantly lowered allergen concentrations. This unexpected result is being tested further in another randomized trial.