A small brown bottle of hydrogen peroxide sits in many medicine cabinets, usually half empty and forgotten. It costs very little, and many people are now using it as a cheap first response to household pests. It can help in some situations, but it has clear limits.
Why It Works
Hydrogen peroxide is water with one extra oxygen atom. On contact with living tissue, it releases oxygen that damages cells, then breaks down into plain water and oxygen. That is why it leaves no chemical film behind. The key word is contact: it only affects what it touches directly.
Cockroaches
Roaches follow scent trails left by other roaches to reach food. Spraying standard 3% peroxide directly on a roach kills it on contact, and spraying along baseboards, cabinet hinges, under appliances and around pipes can break down the trail they follow. Pair this with cleaning up crumbs and sealing gaps, or new roaches will simply find another route.
Bedbugs
Bedbugs hide in mattress seams, box spring edges and gaps near the headboard. Spraying these spots can kill the bugs and eggs the liquid actually reaches. The problem is that many bugs hide deeper than a spray can go, so peroxide is best used at the very first sign of activity. A real infestation needs professional heat or chemical treatment. Let everything dry fully before remaking the bed, and test a small hidden patch first, since peroxide can bleach fabric.
Rats and Mice
Peroxide does not kill rats or mice. Its only role is cleanup. Spraying areas with droppings or urine breaks down scent markers that signal safe territory and helps disinfect the spot. Leave it for five minutes, wipe with paper towels and seal them in a bag. Wear gloves. To actually remove rodents, you need traps, sealed entry points and, for larger problems, a pest professional.