Mothballs are not an effective way to keep cockroaches away. While the chemical fumes they release can kill clothes moths in sealed containers, those same fumes don’t reach concentrations high enough to repel or kill roaches in open living spaces. Worse, scattering mothballs around your home to deter roaches is actually illegal under federal pesticide law and poses real health risks to you, your children, and your pets.
Why Mothballs Don’t Work on Roaches
Mothballs contain one of two active chemicals: naphthalene or paradichlorobenzene. Both release toxic fumes that build up inside airtight containers, which is how they kill clothes moths. The key word is “airtight.” In an open kitchen, bathroom, or basement, those vapors disperse into the surrounding air far too quickly to reach a concentration that would bother a cockroach. Roaches are remarkably hardy insects, and a faint chemical smell in the corner of a room won’t drive them out of a food source or nesting site.
Even if you placed mothballs in a cabinet or closet, the vapor concentration would still fall well short of what’s needed. Cockroaches can simply walk around them, and they’re drawn far more powerfully by food, water, and warmth than they’re repelled by a mild irritant gas.
It’s Illegal to Use Them This Way
Mothballs are registered pesticides regulated by the Environmental Protection Agency. Their labels specify that they must be used only to protect fabrics from clothes moths, placed inside tightly sealed containers. Using mothballs in any way not described on the label, including scattering them in kitchens, garages, attics, or gardens to repel roaches or other pests, violates federal law. The National Pesticide Information Center states plainly that using mothballs outside their labeled purpose “is not only illegal, but can harm people, pets or the environment.”
Health Risks of Mothball Fumes in Living Spaces
The chemicals in mothballs are toxic to humans. If you can smell them, you’re breathing them in. Short-term exposure causes headaches, nausea, eye and nose irritation, and coughing. Naphthalene, the more common active ingredient, can cause a condition called hemolytic anemia, where red blood cells break down faster than your body can replace them. It’s also classified as a possible carcinogen. Long-term exposure can damage your liver and kidneys.
The fumes are heavier than air, so they settle along floors. That makes them especially dangerous for small children and pets, who breathe closer to the ground and are more likely to pick up or chew on the small, candy-like balls. In animals, mothball ingestion causes vomiting, abdominal pain, and lethargy. Larger exposures in pets can progress to anemia, seizures, tremors, and liver or kidney damage. In rare cases, naphthalene poisoning in pets is fatal.
What Actually Works Against Cockroaches
Cockroach control comes down to three things: eliminating what attracts them, sealing entry points, and using targeted treatments that exploit roach behavior. Unlike mothballs, these approaches have strong evidence behind them.
Cut Off Food and Water
Roaches can survive on remarkably little, but they still need moisture and food scraps. Fix leaky pipes and faucets, especially under sinks. Wipe down counters and stovetops every night. Store food in sealed containers, take out trash before bed, and don’t leave pet food bowls out overnight. A roach that can’t find water or crumbs in your home is far more likely to take bait or move on.
Seal Entry Points
Caulk gaps around pipes, baseboards, and where walls meet floors. Seal cracks around door frames and window frames. Cover drains with fine mesh screens. German cockroaches (the small, light brown ones most common indoors) can squeeze through gaps as thin as a credit card, so even small openings matter.
Use Gel Baits and Boric Acid
Gel baits are the most effective DIY option for cockroaches. They work because roaches eat the bait, return to their hiding spots, die, and are then consumed by other roaches, spreading the poison through the colony. Apply small dots of gel bait in cracks, crevices, and along edges where you’ve seen roach activity. For heavy infestations, use three to five spots per ten linear feet of surface; for lighter problems, one to three spots is enough.
Boric acid powder is another proven option. Lightly dust it into wall voids, behind appliances, and under sinks. Roaches walk through the powder, groom it off their legs and antennae, and ingest it. The key is applying a very thin layer. If roaches can see a visible pile of powder, they’ll walk around it. Both gel baits and boric acid are far more targeted than mothballs, with lower risk to household air quality when used as directed.
When Infestations Are Severe
If you’re seeing roaches during the day, finding egg cases, or noticing a musty smell in cabinets, the population is likely large enough that DIY methods alone may not keep up. Professional pest control treatments can reach deep harborage areas inside walls and under appliances that are hard to access on your own. A single professional treatment combined with the sanitation and sealing steps above typically brings a moderate infestation under control within two to four weeks.