Mothballs are not meant to be used outside. Every mothball product registered with the EPA carries label directions specifying use in closed, airtight containers, and using any pesticide in a way that contradicts its label is a federal violation. Despite how commonly people scatter them in gardens, under porches, or around foundations to repel snakes, cats, or rodents, outdoor use is both ineffective and genuinely hazardous to people, pets, soil, and water.
Why Mothballs Don’t Work Outdoors
Mothballs contain very high concentrations of either naphthalene or paradichlorobenzene. These chemicals work by slowly converting from a solid into a toxic gas, a process called sublimation. That gas is what kills clothes moths and fabric-eating insects. The entire mechanism depends on the fumes building up inside a sealed space like a storage bin, garment bag, or trunk. In open air, the vapors disperse almost immediately and never reach a concentration high enough to repel or harm the target pest.
So when you toss mothballs under a deck to keep raccoons away or ring your garden beds to deter snakes, you’re getting almost zero pest control benefit. The chemicals simply drift off on the breeze. What you are getting is a slow release of toxic compounds directly into your yard.
Health Risks to People and Pets
Mothballs look like candy or a small toy to young children, and they smell interesting enough for dogs and cats to investigate. Ingestion is the most common route of poisoning, but simply breathing the vapors or absorbing the chemicals through skin contact can also cause harm.
In animals, naphthalene irritates the digestive tract and almost always causes vomiting, loss of appetite, and abdominal pain. Larger exposures can destroy red blood cells, leading to anemia, pale gums, and difficulty breathing. In rare cases, neurological symptoms like tremors, loss of coordination, and seizures develop. Cats are suspected to be more sensitive than other species to mothball toxicity.
Paradichlorobenzene, the other common active ingredient, primarily causes abdominal pain, vomiting, lethargy, and trembling. Repeated or large exposures can damage the liver and kidneys and eventually cause anemia. A third ingredient, camphor, is the most acutely toxic of the three and can trigger seizures and altered mental states even in small amounts.
For humans, especially children, the risks follow a similar pattern: nausea, headaches, and irritation at low exposures, with the potential for serious blood and neurological effects at higher doses. Mothballs left in open areas where kids play create an ongoing exposure risk that simply isn’t worth taking for a product that won’t accomplish what you’re hoping for anyway.
Environmental Contamination
Mothballs placed outdoors contaminate soil, plants, and water. As they dissolve in rain or irrigation, naphthalene and paradichlorobenzene leach into the ground and can reach groundwater. These are persistent chemicals. Placing them in garden beds means the compounds end up in soil where you may be growing food, and in runoff that flows toward storm drains or nearby waterways. Wildlife that encounters mothballs directly, whether by eating them or nesting near them, faces the same poisoning risks as domestic pets.
The Legal Issue
Mothballs are registered pesticides under federal law. Their labels specify exactly how they can be used: inside sealed containers to protect stored fabrics from moth larvae. Using them in any other way, including scattering them outdoors, violates the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). This isn’t a technicality. The National Pesticide Information Center specifically identifies outdoor use in gardens and around homes as a common misuse.
What to Use Instead
The good news is that for most outdoor pest problems, more effective and safer options exist.
- For snakes: Remove what attracts them. Clear tall grass, brush piles, and rock debris near your home. Seal gaps in foundations larger than a quarter inch. Hardware cloth or fine mesh fencing buried a few inches into the ground can block entry to specific areas.
- For rodents: Eliminate food sources like fallen fruit, open garbage, and bird seed on the ground. Snap traps and bait stations designed for outdoor use are far more effective than mothball fumes that dissipate in seconds.
- For stray or feral cats: Motion-activated sprinklers, citrus peels, or commercial cat-deterrent granules made with plant oils are common approaches. Physical barriers like chicken wire laid flat over garden beds prevent digging.
- For insects in outdoor storage: Cedar blocks, chips, or oil repel moths and other insects without toxic fumes. If you’re storing clothing or textiles in an outdoor shed, place them in airtight plastic bins with cedar or lavender sachets inside.
Cleaning Up Mothballs Already Placed Outside
If you’ve already scattered mothballs in your yard, pick them up wearing gloves and place them in a sealed plastic bag. Don’t crush them or handle them with bare hands. Check with your local waste authority about disposal, as mothballs may qualify as household hazardous waste in your area and shouldn’t go in regular trash. For areas where mothballs have been dissolving into soil over weeks or months, watering the area thoroughly can help dilute surface contamination, but heavily affected soil near vegetable gardens may need to be removed and replaced.