While cockroaches and their bites are not poisonous, allergens in their feces, saliva and body parts can trigger allergic reactions and asthma, especially in children. Statistics from the National Cooperative Inner-City Asthma Study estimate that 23 to 60 percent of urban populations are sensitive to cockroach allergens, as of 2014.
Because most American homes have cockroaches, and cockroaches are nocturnal, physical contact with them and their droppings is much more common than most people suspect. Flying cockroaches leave saliva and other secretions on household surfaces, and they crawl on sleeping people and pets. Residue from their bodies clings to and irritates the skin.
First reported in 1943, a cockroach allergy can cause a rash immediately. Skin tests developed in 1959 confirmed that patients’ allergic reactions were caused by contact with cockroaches. Subsequent research has found that cockroach allergies can also trigger severe asthma attacks.
However, cockroach allergy is not the only health risk associated with cockroaches. When cockroaches emit their strong odor, for example, strong concentrations can alter the flavor of food. In addition, many human illnesses are caused by the bacteria that roaches carry on their bodies and legs. Cockroaches are known to spread 33 kinds of bacteria, including E. coli and Salmonella, as well as six parasitic worms and at least seven other pathogens.