Cockroaches do not like mothballs. The strong chemical odor repels them, and they’ll generally avoid small, enclosed spaces where mothball fumes concentrate. But that dislike is far less useful than it sounds, because mothballs won’t solve a roach problem and using them this way creates real health risks in your home.
Why Roaches Avoid Mothballs
Mothballs are made from naphthalene or paradichlorobenzene, chemicals that slowly release strong-smelling vapors. Those vapors are unpleasant enough to drive many animals away. Cockroaches share that aversion: a mothball tucked behind a stove or under a sink can make roaches steer clear of that specific spot while the smell lasts.
The key phrase is “that specific spot.” Mothballs don’t kill cockroaches or their eggs. They simply make a small area uncomfortable. A roach that encounters the fumes will relocate a few inches away to somewhere without the smell. If you have roaches in your kitchen, dropping a mothball behind the stove doesn’t remove them from your kitchen. It moves them to a different corner of it.
Why Mothballs Fail as Roach Control
Mothballs were designed to kill clothes moths inside sealed, airtight containers like storage bins or garment bags. In that enclosed environment, the vapors build up to lethal concentrations. Sitting loose on a kitchen floor or cabinet shelf, the fumes simply dissipate into the surrounding air without ever reaching a concentration that would kill anything.
This matters because cockroach infestations involve colonies hidden inside wall cavities, behind appliances, and under flooring. Mothball fumes can’t penetrate those spaces. They can’t destroy eggs already laid in cracks. And they do nothing to cut off the food and water sources that attracted roaches in the first place. At best, mothballs act like a temporary “no parking” sign for one small patch of your home while the colony thrives everywhere else.
Health Risks of Loose Mothballs Indoors
Using mothballs outside of a sealed container isn’t just ineffective. It’s actually illegal. Mothballs are a registered pesticide regulated by the EPA, and their labels specify use only in tightly closed, airtight containers. Using them any other way violates federal pesticide law.
The reason for that restriction is health. When naphthalene vapor escapes into your living space, anyone breathing it in is exposed to a chemical that breaks down inside the body and damages cells and tissues. Long-term exposure from mothballs left in open areas, under sinks, or behind appliances means you, your children, and your pets are inhaling those fumes continuously. Mothballs should never be placed near food or food preparation areas, which is exactly where most people want to repel roaches.
Children and pets are especially vulnerable because they spend more time on floors, are more likely to touch or mouth a mothball, and their smaller bodies are more sensitive to the chemical exposure. The health trade-off simply isn’t worth a minor, temporary deterrent effect on roaches.
What Actually Works Against Cockroaches
Effective roach control targets the colony, not just the individual bugs you see. The approaches that work share one thing in common: they kill roaches rather than nudging them a few inches sideways.
- Gel baits: These contain a slow-acting poison mixed with food attractants that roaches eat willingly. The roach carries the toxin back to the colony, where it spreads to other roaches. Gel baits can be placed in sensitive areas like kitchens near food and dishes, spots where sprays wouldn’t be safe. They pose minimal risk to people and pets when applied correctly in small dots in cracks and crevices.
- Boric acid: A powdered mineral that damages a roach’s digestive system when ingested. Research on boric acid gel formulations shows effectiveness increases with concentration, and the compound works as a stomach toxin rather than a repellent, meaning roaches don’t avoid it. A light dusting in wall voids, behind outlet covers, and under appliances reaches the hidden spaces where colonies live.
- Eliminating food and water: Roaches stay where they can eat and drink. Fixing leaky pipes, wiping down counters nightly, storing food in sealed containers, and emptying pet water bowls before bed removes what drew them in. Without these basics, any treatment is fighting an uphill battle.
- Sealing entry points: Caulking gaps around pipes, filling cracks in baseboards, and adding weather stripping to doors cuts off the routes roaches use to enter from neighboring units or the outdoors.
For a light problem (seeing one or two roaches occasionally), gel baits and sanitation changes are often enough. For a heavier infestation, especially in apartments or older buildings with shared walls, professional treatment may be necessary because the colony’s source could be in spaces you can’t access yourself.
The Bottom Line on Mothballs and Roaches
Roaches dislike the smell of mothballs, and that fact has fueled a home remedy that’s been passed around for decades. But disliking something and being eliminated by it are very different outcomes. Mothballs won’t kill a single roach, won’t touch eggs or hidden colonies, and will expose your household to toxic fumes in the process. The chemicals that actually end roach infestations work by being eaten, not smelled.