How do cockroaches cause asthma?

Cockroaches are a very significant cause of asthma. They are common in multiple-family dwellings in most major U.S. cities, including expensive apartment buildings, as well as in single-family homes in warm, humid parts of the country. It is estimated that one visible roach represents a population of a hundred roaches living in the walls. Many parts of the cockroach are allergenic, including their bodies, urine, feces, and saliva. When they die, their bodies break down and they become part of the house dust. In old apartment buildings, there may be many years' roach allergen in the dust, so anyone living in a home where there have been roaches at any time is at risk.

While roach allergen concentration is highest in the kitchen, the bedroom is a more important venue for exposure simply because we spend so much time in it. An estimated 6 million U.S. bedrooms contain enough cockroach allergen to cause asthma.