Cockroaches
Other than being disgusting, disturbing creatures to have scuttling around the home, cockroaches are also carriers of pathogens such as harmful bacteria (Salmonella) and unhealthy fungi. As they walk on food or countertops, they can transfer these organisms to be ingested by people living in the home.
To make matters worse, the salvia, feces, outer covering, and eggs of cockroaches have been reported by Agricultural Research Magazine to be highly allergenic to those with asthma and respiratory conditions. These allergens can linger even after the infestation has been eliminated, with studies showing that the allergens are still present even years later. And with a single cockroach being able to produce as many as 500 young in a year, there’ll be a lot of these allergens to go around!
The German Cockroach and the brown-banded cockroach are especially problematic in the United States, although there are many species known to infest homes. They can feed on nearly anything, including grease, hair, food particles, other dead cockroaches, or nearly anything else.