Cockroaches are among the most feared insects for many people. After killing them, many quickly flush them down the toilet, sometimes even when the cockroaches aren’t completely dead yet. However, this “out of sight, out of mind” approach can lead to serious problems. Japanese experts warn against flushing live cockroaches directly into the toilet, as this simple act could cause a dangerous “insect crisis.” They also share the proper ways to kill cockroaches safely.
According to Japanese media outlet Grape, Dr. Hiroaki Hayashi, director of a surgical and internal medicine clinic in Fukuoka, explains that while it’s important to remove pests quickly, flushing them down the toilet is not a good choice. Cockroach bodies, droppings, and shed skins are potent allergens. Moreover, live cockroaches can survive underwater for about 40 minutes by closing their breathing holes on both sides of their bodies. Flushing them won’t kill them immediately. Female cockroaches could even lay eggs inside the pipes, leading to eggs hatching and new infestations emerging from the drains. For these reasons, experts generally advise against flushing cockroaches down the toilet.
Dr. Hayashi recommends a three-step method to safely and hygienically kill cockroaches:
- Use a fast-acting insecticide spray or strike the cockroach forcefully to stop it from moving.
- Collect the cockroach with a tissue or paper cup, then seal it in a plastic bag and dispose of it as combustible trash—avoid handling it with bare hands.
- Remove food debris and sources of moisture, seal any cracks or gaps in the home, and consider using insecticide baits if cockroach activity is frequent.
Dr. Hayashi also notes that high-concentration alcohol is an effective cockroach killer that evaporates quickly, is easy to obtain, works fast, and has minimal impact on the surrounding area. He advises confirming the cockroach is dead before sealing and disposing of it properly as combustible waste.
