Skip Navigation

Your Environment. Your Health.

Cockroach Allergen Intervention

The Cockroach Allergen Intervention Study: A Multi-Faceted Approach

Evidence suggests that exposure to cockroach allergen might be the most important risk factor for asthma in inner-city households. However, cockroach extermination alone does not appear to be effective in lowering allergen levels and there are no proven methods for allergen abatement in infested homes. Although several studies that combined cockroach extermination with cleaning demonstrated reductions in allergen levels, none was successful in lowering cockroach allergen levels below clinically relevant thresholds.


Photos of various cockroaches
The cockroach in the center is a mature female with an attached egg case. To her left is a mature male, and to her right are nymphs in various stages of development.

The objective of the Cockroach Allergen Intervention Study was to evaluate the efficacy of an intervention to abate cockroach allergen in low-income, urban homes. The intervention involved occupant education, cockroach extermination, and professional cleaning. The goal was to reduce mean cockroach allergen levels below the thresholds for allergic sensitization and asthma morbidity.


At the end of 6 months, cockroach numbers and allergen levels decreased significantly in the intervention homes compared to the control homes. We decided to evaluate whether the cockroach allergen reductions could be maintained for an additional 6 months, and re-enrolled the homes for an additional 6 months of follow-up. The control homes had been promised extermination at the end of the initial 6 months of follow-up and were crossed over into an extermination only arm at month 6. Unexpectedly, and in contrast to other published studies, cockroach control alone significantly lowered cockroach allergen levels in crossed-over homes. This finding raised the possibility that cockroach control alone could significantly lower cockroach allergen. A study to confirm these findings has been implemented, and is described in the following section.


Cockroach Allergen Reduction Through Cockroach Control Alone

Interior of cabinet with cockroach body parts and feces
Cockroaches and cockroach body parts and feces in the interior of a kitchen cabinet in one of the study homes.

Contrary to other reports in the literature, results from our cockroach allergen intervention trial suggested that cockroach extermination alone—without professional cleaning or occupant education—can reduce cockroach allergen levels in inner-city homes. This was an important finding because extermination alone would be much less expensive and easier to implement than a more comprehensive intervention; however, this result needed to be replicated.


Sixty cockroach-infested, multi-unit rental homes were randomly assigned to either a control group or to one of two treatment groups. The Treatment-1 group is receiving insecticide bait placement by Dr. Coby Schal and the urban entomology staff in his lab at North Carolina State University. The Treatment-2 group is receiving extermination from 1 of 4 commercial pest control companies randomly assigned to the homes. The homes will be followed for one year, and all follow-up visits will be completed by early 2006. The results from this study, if they prove to be consistent with our previous work, will become a component of our future asthma prevention trials.


Publications & Questionnaires

See Related Publications for further information about these studies.


The questionnaires used in the survey are available as PDF files:

Back to Top