Cockroaches are insects that have been around for hundreds of millions of years and are found in many locations around the world. Cockroaches are well-known pests that adapt easily to a variety of environments. They usually run away from light and are mainly active at night. Cockroaches contain an allergen protein which is harmful for many individuals. An allergen is a substance which causes an allergic immune reaction. The saliva, wastes and body parts of the cockroaches are allergens and even dead cockroaches can cause allergic reactions. Cockroach allergy is diagnosed with the use of allergy testing. Skin testing and blood testing for IgE to cockroach are the two ways to diagnose cockroach allergy.