Why Experts Warn Against Using Mothballs to Deter Mice

Stack of white round mothballs on a wooden surface — Credit:
Getty Images

Mothballs are not effective at deterring mice and can pose serious health risks to people and pets.
Seal entry points larger than a quarter inch with wire screen or steel wool, and use high-quality door sweeps to prevent mice from entering your home.
Store food and organic fertilizers in sealed containers, and remove clutter to make your home less attractive to mice

If you’re trying to keep mice away, a well-meaning friend or family member might suggest mothballs as an easy-to-use deterrent. However, this old-school trick should stay in the past. "Mothballs are made for clothes in sealed containers—not for open areas where rodents live," says Trent Frazer, lead entomologist at Aptive Pest Control. "While they contain strong-smelling chemicals like naphthalene or paradichlorobenzene, mothballs do not consistently drive mice away," says Frazer.

Below, our pest control experts weigh in on safer and more efficient ways to deal with mice and how to know when you need a professional’s help.

Trent Frazer, lead entomologist at Aptive Pest Control
Derrick Clay, district manager with Trutech Wildlife Service
Garrett Thrasher, co-owner and general manager at Thrasher Termite & Pest Control of So Cal, Inc.
Dan Latini, owner of Dan Can Home Services

The Risks of Mothball Use

Mothballs work through their chemical makeup, usually containing odorous toxicities like naphthalene or paradichlorobenzene. "These chemicals slowly turn into gas, which kills moths and other insects," Frazer explains. However, they aren't an effective deterrent to mice. "Studies have shown that mice often ignore the smell once they get used to it, especially if there's food or shelter nearby," he says.

Not only will mothballs fail to deter mice, you may also be putting your own safety (and that of your family) at risk: The gas mothballs emit is harmful to both people and pets. "Breathing it in over time can cause headaches, dizziness, and even serious health issues like liver and kidney damage," says Frazer. "If a child or pet eats a mothball, it can be dangerous."

Moreover, you may even be committing a federal offense. "Because mothballs are registered with the U.S. Environmental Protection Agency, it is a federal law violation to use them in a manner inconsistent with the label," warns Derrick Clay, district manager with Trutech Wildlife Service. And you definitely won't find "mice control" on its recommended uses.

Safer Alternatives to Keep Mice Away

The best mouse deterrent is prevention, says Clay. Since mothballs are proven to be ineffective (and harmful), here are some safer alternatives to consider.

Seal Up Entry Points

"Seal any entry points greater than a quarter inch with wire screen or coarse steel wool," says pest control expert Garrett Thrasher. "Make sure to seal below doors as well with high-quality door sweeps." Avoid caulking, he adds, as mice can easily chew through it. Pay attention to the seal at the bottom of your garage door, too. It'll need replacing as it wears.

Make Food Inaccessible

Store all food (including pet food) in sealed containers, wipe up crumbs, and take out the trash regularly. And don't forget about your compost and garden: Organic fertilizer contains ingredients mice and rats like, like blood meal or bone meal. “Store fertilizer in a metal bucket with a tight-fitting lid to deter mice from looking for a free meal in your shed or garage,” Thrasher says.

Clean Up Indoor Clutter

Removing clutter is essential for successful at-home pest and rodent control. "Without food or places to hide, your home becomes a much harder place for mice to live," Frazer says.

Tidy Your Landscaping

Keep your grass cut short and limit leaf piles in the yard. “This can take away safe harborage for mice and other pests and not attract them to your home,” says extermination professional Dan Latini, owner of Dan Can Home Services.

Latini also advises keeping tree limbs trimmed to around two feet away from the home. "Rodents are great at jumping, and having tree limbs on your roof can be an easy access point for mice and others to gain entry to your home," he explains. "Once they have an entrance, they have complete access to your home and will use your utility lines and plumbing like highways to navigate through your home."

When to Call a Professional

If you’ve sealed up your home's entry points and are still noticing signs of mouse life (e.g. droppings, scratching noises, or nests), Frazer suggests calling a rodent control professional. “Mice breed quickly, and just a few can turn into a serious problem fast,” he warns.

In fact, one single mouse can give birth to five to 10 litters a year, with each litter consisting of six to eight mice. "Pest control experts can find where they’re getting in," Frazer says, "and create a treatment plan to remove them and keep them from coming back."