Mothballs are not an effective squirrel repellent, and using them for that purpose is both hazardous and legally questionable. While the strong odor can temporarily annoy mammals, squirrels quickly tolerate the smell at any concentration safe for humans. Professional wildlife controllers are frequently called in after homeowners discover mothballs had zero effect on their squirrel problem.
Why Mothballs Don’t Work on Squirrels
Mothballs contain one of two chemicals: naphthalene or 1,4-dichlorobenzene. Both produce a strong vapor that can irritate mammals, including squirrels. The catch is that you need extremely high concentrations of the odor to actually drive an animal away. In an attic or crawl space, reaching those concentrations means the fumes would also be unbearable (and dangerous) for you and your family. In open outdoor spaces, the vapor simply disperses too quickly to bother a squirrel at all.
The Internet Center for Wildlife Damage Management notes that it is “extremely common” for professional animal damage controllers to be hired after homeowners tried mothballs and found them completely ineffective. Squirrels are persistent, adaptable animals. A bad smell is not enough to keep them away from a reliable food source or a warm nesting spot.
Health Risks of Mothball Misuse
The bigger problem with scattering mothballs around your yard, garden, or attic is the real harm they cause to people and pets. Naphthalene vapor exposure causes headaches, nausea, dizziness, and vomiting. At higher exposures, it can trigger hemolytic anemia, a condition where red blood cells break apart and can no longer carry oxygen properly. Pregnant women who inhaled mothball vapors or ingested naphthalene have given birth to babies with this same type of anemia.
Children are especially vulnerable. Mothballs can look like candy to a small child, and ingestion causes diarrhea, fever, abdominal pain, and discolored urine. Even indirect contact is risky: infants have developed anemia simply from wearing clothes or being wrapped in blankets that were stored with mothballs and not washed afterward. People with a certain inherited enzyme deficiency face an even greater risk of anemia from exposure.
Pets are at risk too. Dogs that eat naphthalene mothballs can develop lethargy, vomiting, diarrhea, loss of appetite, and tremors. A single mothball contains enough chemical to seriously harm a small dog or cat.
It’s Also Against the Law
Mothballs are registered pesticides, and their labels specify use only in enclosed containers for protecting stored fabrics from moths. Scattering them in your garden, attic, or around your foundation to repel wildlife is off-label use, which violates federal pesticide law. The National Pesticide Information Center specifically warns against using mothballs outdoors, noting they can contaminate soil, plants, and water in addition to harming children, pets, and wildlife.
What Actually Keeps Squirrels Out
The only reliable long-term solution for squirrels is physical exclusion: sealing the entry points they use to get into your home. This works because squirrels need surprisingly small gaps to squeeze through, and blocking those gaps with the right materials stops them permanently.
Half-inch hardware cloth is the standard material for closing off vents, soffits, and other openings. It’s strong enough that squirrels can’t chew or tear through it. For larger or more exposed areas, galvanized sheet metal attached with screws resists removal by animals. Stainless steel mesh is even stronger and won’t rust over time. Smaller cracks and gaps can be sealed with caulk, copper gauze, or foam insulation.
Chimneys are a common entry point. Many metal chimney caps can be enclosed with half-inch hardware cloth, though any covering needs to meet local fire code requirements. If squirrels are accessing your roof by running along power lines, you can contact your utility company about installing barriers on the lines.
Before You Seal Entry Points
One critical step: make sure no squirrels are still inside before you close up their entry holes. Trapping an animal inside your walls or attic creates a much worse problem. If you’re not sure whether an opening is actively being used, monitor it for at least two days. Stuff newspaper into the hole, tape cardboard over it, or use duct tape. If an animal is coming and going, you’ll see the material disturbed. Any squirrels currently living inside need to be removed first, either by giving them a one-way exit or by hiring a wildlife control professional.
Other Deterrents Worth Trying
If squirrels are raiding bird feeders or digging in your garden rather than entering your home, a few practical changes help more than any chemical repellent. Switching to squirrel-proof bird feeders with weight-activated perches cuts off their food motivation. Trimming tree branches back at least six to eight feet from your roofline removes their easiest access route. Covering garden beds with wire mesh lets plants grow through while keeping squirrels from digging.
Commercial capsaicin-based repellents (made from hot pepper extract) can deter squirrels from specific spots like bulb beds or bird seed, though they need reapplication after rain. These are at least labeled for outdoor use, unlike mothballs, and pose far less risk to children and pets.