Cockroaches are usually in the walls and under the cupboards and cabinets inside homes and apartments. Most of the time, no one even knows they are there. They usually only come out at night. What happens, though, is that they lay thousands of eggs and leave tons of waste behind. They also leave a powdery residue behind when they die and their bodies decompose. These things all can be breathed in and can cause allergies. You can eliminate cockroaches with traps and by making sure all food items are sealed up tight. Never leave dirty dishes in the sink, and always clean up any food mess in the kitchen.