In every human population, there is a segment of people with immune systems that respond to innocuous substances like pollens or dust. Cockroaches are known to trigger allergic responses in about 12% of individuals with no other allergies. Additionally, an estimated one-third of individuals sensitive to other allergens are also allergic to cockroaches. Allergens: Cockroach faeces, saliva, bodies, and casts contain allergens which can trigger allergic responses in susceptible individuals. Particles of these allergens can become airborne inside a home. People who live in or visit chronically infested dwellings may breathe the dust in. Individuals with cockroach allergies may experience sinus congestion, rash, sore throat, and irritation of the eyes. Most allergies are seasonal, and experiencing symptoms year-round may indicate a cockroach infestation. Cockroach allergies may aggravate asthma conditions in some asthmatic individuals. Asthma: In addition to troubling those with asthma already, cockroaches can also cause individuals to develop the condition. Approximately three million Canadians have asthma, and cockroaches are a significant cause of the respiratory condition. Children have greater susceptibility to cockroach allergens and more allergen exposure, which puts them at the greatest risk for developing asthma from these pests. Individuals living in inner city areas are at increased risk of developing asthma. It is unclear whether cockroaches are the cause, but it is theorized to be the reason for higher asthma rates in cities since cockroach infestations are more prevalent in urban environments.