"Doc, I don't have cockroaches. Why is my skin test to cockroach positive?" A downtown Chicago businessman who owns a home in an upscale Chicago suburb asked this question earlier this year.
I'll start with an update on this topic
Recent asthma research has focused on a common allergen often briefly discussed in reports on indoor allergy triggers. Cockroaches are considered the most disgusting creatures that may co-inhabit our homes but are chiefly regarded as a problem of city-dwellers that live in poor income housing. Studies of inner-city asthmatics have identified a high prevalence of cockroach sensitivity as well as a high level of cockroach allergen in their homes.
A study conducted by Dr. Daniel Remick identified cockroaches as the major allergen trigger in inner city children who have asthma. Dust samples were collected from homes in poverty stricken areas in Detroit, Michigan. The dust samples were used to make an extract by adding water and spinning the mixtures in tubes in order to separate out the larger solid material. The extract was analyzed and found to mainly have cockroach proteins in them (dust mite proteins were not as high).
Next, laboratory mice were sensitized by injecting them with the extract. Later on, the sensitized mice were exposed to air containing the same dust particles collected from the homes. The sensitized mice begin to have difficulty breathing and wheezing. Mice that were not sensitized by injection did not have breathing problems.
According to Dr. Remick, the sensitized mice also had lung infiltrates (after inhaling the dust collection) of a certain type of white blood cell typically seen in people who have asthma.
Why is this research meaningful?
Dr. Remick and his team of scientists now have an animal model for the investigation of new medications for asthma treatment. Mice that have been sensitized to real life indoor allergy triggers found in homes are more desirable for research. Their response to various drugs may better reflect the human response.
Are suburbanites and people who live in rural areas free of cockroach exposure?
A study of 339 asthmatic children in suburban and rural Baltimore, Maryland yielded some surprising results (American Academy of Pediatrics -2004). Environmental technicians were sent to their homes and took dust samples which were examined for dog, cat dust mite and cockroach proteins.
Thirty percent of suburban-rural homes were found to have measurable cockroach protein (40% had measurable pet proteins). Five percent of the same homes were considered to have cockroach infestation. Thirty five percent of urban dwellers were skin test sensitive to cockroach and twenty-one percent of suburban-rural dwellers.
The report concluded the presence of cockroach allergen is higher in suburban middle class homes than previously thought. Furthermore low levels of cockroach allergen exposure may lead to sensitization.