Mothballs do not reliably repel chipmunks, and using them for that purpose is both ineffective and illegal in the United States. Mothballs are registered pesticides whose labels restrict them to use against clothes moths and carpet beetles in enclosed containers, not as outdoor wildlife deterrents. The idea persists because mothballs produce a powerful, unpleasant odor, but the chemistry that makes them stink indoors works against them outside, and no credible evidence supports the claim that chipmunks are deterred by the smell for any meaningful length of time.
What Mothballs Actually Are
Mothballs are solid pesticide formulations, not household deodorizers or generic repellents. Their active ingredients are either naphthalene or paradichlorobenzene, both of which slowly transition from a solid to a gas at room temperature through a process called sublimation. That vapor is what kills moth larvae eating through your wool sweaters. It works because a sealed garment bag or airtight storage container traps the vapor at concentrations high enough to be lethal to insects over time.
Because these chemicals are classified as pesticides, their product labels are legally binding. The label specifies where and how the product can be used, and those directions carry the force of federal pesticide law.1EDIS. The Facts about Mothballs This is not a technicality or a suggestion. The Environmental Protection Agency registers mothballs under the Federal Insecticide, Fungicide, and Rodenticide Act, and using any registered pesticide in a manner inconsistent with its labeling is a violation of that law. No mothball product sold in the U.S. is labeled for repelling chipmunks, squirrels, snakes, or any other wildlife.
Why the Smell Seems Like It Should Work
Chipmunks have a keen sense of smell. They use it to find buried food caches, detect predators, and navigate their home ranges. So the logic feels intuitive: if a mothball smells terrible to a human nose, surely it would drive away a small rodent. People toss mothballs into garden beds, around foundations, near burrow entrances, and under porches with this reasoning in mind.
The problem is that outdoors, the vapor never reaches a concentration that would do much of anything. Naphthalene is highly volatile in open air. Research on naphthalene in soil and atmospheric systems shows that the compound readily volatilizes from surfaces and disperses rapidly, especially with any air movement.2PubMed Central. Assessing Wildfire Impact on Diffusive Flux of Parent and Alkylated PAHs: A Pilot Study of Soil–Air Chemical Movement before, during, and after Wildfires In a sealed container, that sublimation builds up a lethal dose for insects. In your yard, the vapor drifts away almost immediately. What you smell when you walk past a mothball in a garden bed is the chemical leaving, not accumulating.
Even in the brief window when a freshly placed mothball gives off a noticeable odor, there is no scientific evidence that chipmunks respond to it by permanently relocating. An animal startled by a new, strong smell near its burrow might avoid the spot for a few hours or a day, but chipmunks are territorial and habitual. They have established tunnel systems, food stores, and nesting sites. A bad smell near the front door of their burrow is not enough to make them abandon their home, any more than a bad smell outside your front door would make you move to a new house.
The Legal Problem Is Real
Scattering mothballs outdoors is not a gray area. Because mothball active ingredients are registered pesticides, using them anywhere other than in the manner specified on the label is a federal violation. State environmental agencies have issued warnings and, in some cases, fines to homeowners and businesses caught using mothballs as animal repellents or snake deterrents.
The label restriction exists for good reason. Mothball chemicals are toxic to far more than just moths. Naphthalene is classified as a possible human carcinogen. Paradichlorobenzene has been associated with neurological effects in people exposed to high concentrations over long periods. Scattering these chemicals across a yard, where children crawl, dogs sniff, and rain washes the residue into soil and groundwater, creates exposure risks the product was never designed to pose.1EDIS. The Facts about Mothballs
If you are thinking, “Who would ever know?” keep in mind that mothballs dissolve slowly and leave a persistent chemical signature in soil. A neighbor who complains about the smell, a pet that gets sick, or a child who picks up a mothball thinking it is a candy can all trigger investigations. And the liability falls squarely on the person who applied the pesticide off-label.
What Mothballs Do to Your Yard
Even setting aside legality and effectiveness, mothballs scattered outdoors cause measurable environmental harm. Naphthalene does not simply evaporate and vanish. Some of it dissolves into soil moisture, where it persists and affects organisms living in the top few centimeters of soil. Research on naphthalene contamination in soil has shown that the compound stays concentrated in the upper layers and causes serious damage to earthworms, including intestinal tissue destruction, severe oxidative stress, and disruption of their gut microbial communities and metabolic pathways.3PubMed. Toxic effects of representative petroleum contaminants on earthworms (Eisenia fetida) under rainfall conditions
Earthworms are not a minor concern. They are a cornerstone of healthy garden soil, aerating the ground and breaking down organic matter. Killing them off with scattered naphthalene to chase away a chipmunk that will likely return in a few days is a poor trade. Rain can also carry dissolved naphthalene into storm drains or shallow groundwater, potentially affecting aquatic organisms downstream. You are not just failing to repel a chipmunk; you are poisoning the soil ecosystem you depend on for healthy plants.
Risks to Children and Pets
Mothballs look like small white balls or tablets. To a toddler, they can resemble candy. To a dog, they are an interesting object to chew. Ingestion of even a single naphthalene mothball can cause serious poisoning in small children and pets, with symptoms including nausea, vomiting, abdominal pain, and in severe cases, hemolytic anemia, a condition where red blood cells break down faster than the body can replace them. Cats are especially sensitive to naphthalene because they lack certain liver enzymes needed to metabolize the compound.
Paradichlorobenzene mothballs are somewhat less acutely toxic if swallowed, but chronic exposure to the vapors has been linked to neurological symptoms in humans, including dizziness, headaches, and in extreme cases, damage to the nervous system. These risks are manageable when the product is used as directed, sealed inside a container in a closet. They become unacceptable when mothballs are scattered across open ground where unintended contact is essentially guaranteed.
What Actually Deters Chipmunks
If you have a chipmunk problem around your home or garden, the approaches that actually work fall into a few categories: physical exclusion, habitat modification, and targeted trapping.
- Hardware cloth: Quarter-inch mesh hardware cloth buried around garden beds, along foundations, or over bulb plantings physically prevents chipmunks from digging through. This is the single most reliable method for protecting specific areas.
- L-shaped barriers: For foundation protection, burying hardware cloth in an L-shape along the base of your home, extending outward about a foot underground, blocks burrowing attempts without chemicals.
- Removing food sources: Bird feeders are the number-one chipmunk attractant for most homeowners. Spilled seed on the ground is an open invitation. Switching to a caged feeder, using seed blends chipmunks ignore, or temporarily removing feeders altogether can dramatically reduce the local chipmunk population over a season.
- Reducing cover: Chipmunks prefer areas with stone walls, wood piles, dense ground cover, and brush near food sources. Clearing these staging areas away from your house and garden makes your yard less attractive to them.
- Live trapping: Where legal, small live traps baited with sunflower seeds or peanut butter can catch chipmunks for relocation. Check your local regulations first, as some states restrict relocation of wildlife or require specific trap types.
Commercial repellent sprays containing capsaicin or predator urine have mixed reviews. Some homeowners report temporary success, but the evidence for their long-term effectiveness is thin, and they require frequent reapplication. They are at least legal to use outdoors, unlike mothballs.
Why Chipmunks Are Hard to Discourage
Part of the reason people resort to desperate measures like mothballs is that chipmunks are genuinely persistent. Eastern chipmunks, the species most commonly encountered in North American yards, are semi-fossorial, meaning they spend a significant portion of their lives underground. Their burrow systems can extend 10 to 30 feet in length with multiple entrances, food storage chambers, and nesting areas. A single chipmunk may cache several pounds of seeds and nuts in these underground pantries over the course of a fall season.
This investment in infrastructure makes chipmunks reluctant to leave. Research on chipmunk populations in fragmented habitats has shown that even when conditions are suboptimal, such as in small isolated woodlots rather than continuous forest, chipmunks persist and maintain their populations.4Oxford Academic. Effects of Forest Fragmentation on Population Attributes of White-Footed Mice and Eastern Chipmunks They adapt rather than relocate. If a chipmunk has chosen your property, it is because the site offers the combination of shelter and food it needs, and a bad smell is unlikely to override those survival imperatives.
Chipmunk population density also fluctuates with mast years, the periodic heavy seed production by oak and beech trees. In years when acorn production is high, chipmunk populations boom the following spring. If it seems like your chipmunk problem got worse overnight, it probably did, and no amount of mothballs would have prevented it.
Other “Home Remedies” That Don’t Work
Mothballs are not the only ineffective chipmunk deterrent that circulates online and in gardening forums. A few others deserve mention because they share the same flawed logic: if it smells strong or tastes bad, animals will flee.
Ammonia-soaked rags placed near burrow entrances follow the same reasoning as mothballs. The smell dissipates quickly outdoors, and the chipmunk simply uses a different entrance. Dryer sheets, another popular suggestion, have no repellent properties against any rodent once the fragrance fades, which happens within a day or two in outdoor conditions. Ultrasonic repellent devices marketed for rodents have been tested repeatedly and shown to have no lasting effect on chipmunk or squirrel behavior. The animals may initially startle at a new noise, but they habituate to it within days.
Cayenne pepper sprinkled on garden beds can deter chipmunks from digging in that specific spot temporarily, since capsaicin is irritating to mammals. But rain washes it away, and the chipmunk simply digs two feet over. The effort-to-result ratio is poor unless you are protecting a very small, specific area and willing to reapply after every rainfall.
The common thread is that chipmunks are intelligent, adaptable animals with strong site fidelity. Short-term annoyances do not overcome the biological imperative to stay near an established burrow with food stores. Effective control almost always comes down to making the habitat physically unsuitable rather than chemically unpleasant.
When Professional Help Makes Sense
Most chipmunk situations are manageable with the DIY exclusion methods described above. But there are cases where calling a licensed wildlife control operator is worthwhile. If chipmunks are burrowing under a concrete patio slab, a porch, or your home’s foundation, the structural risk from undermining can be real. Settling and cracking caused by extensive tunnel systems underneath a slab is not unheard of, particularly in older homes with shallow footings.
A wildlife professional can assess the extent of the burrow system, recommend exclusion methods appropriate for the structure, and in some states, use lethal control methods that are not available to homeowners. They can also help determine whether the burrowing animal is actually a chipmunk rather than a woodchuck or vole, which require different management strategies.
If you live in an area where chipmunks are especially abundant and you have tried exclusion without success, a professional can also advise on whether your property has features that are unusually attractive to chipmunks, such as rock retaining walls with gaps, dense juniper plantings, or compost bins placed near the house. Sometimes a relatively simple landscape change reduces the problem more effectively than any repellent or trap ever could.