Do Mothballs Keep Mice Away? Why This Old Hack Is a Bad Idea

Do mothballs keep mice away? It is one of the oldest tricks passed around for attics, garages, cabins, and parked cars, and it is still repeated online every winter. The idea sounds logical: mothballs smell strong, mice have sensitive noses, so scatter a few and the mice will leave.

The problem is that mothballs are a pesticide with a very specific legal use, and keeping mice away is not on the label. Here is what the label allows, why the hack is risky, and what to do instead.

The Short Answer: Do Mothballs Keep Mice Away?

No, you should not use mothballs to keep mice away. Mothballs are registered pesticides made to control clothes moths inside airtight containers. Mice are not a listed target on the label we reviewed, and federal law says it is a violation to use a pesticide in a manner inconsistent with its labeling. The Georgia Department of Agriculture puts it plainly: use mothballs only for listed pests, usually clothes moths, and off-label use is illegal.

On top of the legal issue, the vapors are a health concern for people and pets, and mothballs do nothing about the gaps mice use to get inside.

What Mothballs Actually Are

According to the National Pesticide Information Center (NPIC), mothballs are pesticides, and the two active ingredients used in them are naphthalene and paradichlorobenzene. They are regulated by the EPA. Mothballs are solid, but they slowly turn into a gas. Inside an airtight container, that vapor builds up to a level that controls clothes moths and their eggs and larvae.

That design matters. Mothballs are meant for a small, closed space like a garment bag or trunk, the opposite of an attic, garage, or engine compartment.

What the Label Says

The EPA explains that, unlike most product labels, pesticide labels are legally enforceable, and every one carries the statement: "It is a violation of Federal law to use this product in a manner inconsistent with its labeling." In the EPA's words, the label is the law.

As an example, we read the EPA-accepted master label for a common naphthalene mothball product (EPA Reg. No. 1475-74), which is published on the EPA website. Its directions say the product is for clothes moths, their eggs and larvae in clean, airtight containers such as chests, trunks, garment bags, and storage closets. It says not to use containers that allow vapors to escape into occupied rooms, and to keep the product out of reach of children. Mice are not listed anywhere as a target.

NPIC states that using mothballs in a way not specified by the label is not only illegal but can harm people, pets, or the environment. The Georgia Department of Agriculture lists common misuses that people should avoid, including:

  • Scattering mothballs in attics, basements, or crawl spaces
  • Placing them in drawers, under furniture, or in vehicles
  • Trying to repel wildlife, squirrels, snakes, or raccoons

In other words, the exact places people put mothballs to keep mice away are the places the label does not allow.

Why the Hack Is Risky

For People

The Georgia Department of Agriculture notes that if you can smell mothballs, you are already being exposed to the chemicals. Short-term exposure to the vapors may cause headaches, nausea, dizziness, eye, nose, or throat irritation, and breathing difficulties. NPIC adds that exposure to large quantities of naphthalene or paradichlorobenzene can lead to headaches, nausea, vomiting, or diarrhea.

For Children

The EPA warns that illegal naphthalene mothballs are hazardous to young children because they can easily be mistaken for candy.

For Pets

The ASPCA says all mothballs will cause stomach upset if eaten, and certain types are also a risk for liver and kidney injury, damage to red blood cells, or neurologic signs like tremors and seizures. Mothballs on a garage floor or in a crawl space are within easy reach of a curious dog or cat.

What to Do Instead: A Better Plan

Step 1: Seal Entry Points

The CDC says mice can fit through a hole about 1/4 inch wide, roughly the width of a pencil. Fill small holes with steel wool held in place with caulk, and use hardware cloth, metal sheeting, or cement for larger openings. Our guide to steel wool for mice walks through it step by step.

Step 2: Remove Food and Shelter

The CDC recommends storing food in containers with tight lids, putting pet food away, and keeping garbage in sealed containers.

Step 3: Trap Mice That Are Already Inside

For mice already in the house, the CDC recommends traditional snap traps placed where you see signs of activity, and advises against glue traps and live traps. Keep traps away from children and pets.

Step 4: Use a Product Labeled for the Job

If you want a scent deterrent, choose one sold as a rodent repellent and follow its directions. Peppermint oil and cinnamon oil are on the federal list of minimum risk pesticide ingredients, but the EPA does not review these exempt products, so treat them as an extra layer, not a fix. Our guide to natural mouse repellents compares the options.

Step 5: Call a Professional When Needed

If you see droppings in several rooms or activity keeps coming back after you seal, contact a licensed pest control professional.

If You Already Put Mothballs Out

Wear gloves, pick them up, and check the product label for disposal instructions. The Georgia Department of Agriculture says not to flush mothballs, burn them, or throw them in household trash. Take unused mothballs to a household hazardous waste collection site, and contact your local solid waste authority for instructions. If a child or pet may have swallowed one, call your doctor, your veterinarian, or 911 right away.

Cheat Sheet

  • Mothballs are pesticides with naphthalene or paradichlorobenzene.
  • Labels cover clothes moths in airtight containers, not mice.
  • Using a pesticide inconsistently with its label violates federal law.
  • Attics, crawl spaces, garages, and vehicles are common misuse sites.
  • If you can smell mothballs, you are being exposed to the vapors.
  • Seal gaps, remove food, and trap mice already inside instead.

Where BioGuard Fits

We sell BioGuard Natural Rodent Repellent, a pack of 12 scent balls infused with peppermint and cinnamon essential oils. If you were reaching for mothballs to protect a garage, shed, storage area, or car engine compartment, this is a product designed for that kind of spot. It works best after you seal entry points, should be replaced every 4 to 6 weeks (sooner after heavy rain outdoors), and must be kept away from children, pets, and food. It is a repellent, not a removal product, and results vary.

Frequently Asked Questions

Is it illegal to use mothballs to keep mice away?

Using any pesticide in a way that is inconsistent with its label violates federal law, according to the EPA. The Georgia Department of Agriculture states that off-label use is illegal and could result in penalties.

Do mothballs keep mice out of the attic?

Scattering mothballs in attics, basements, or crawl spaces is one of the misuses the Georgia Department of Agriculture warns against. Seal roof line gaps and cover vents with hardware cloth instead.

Can I put mothballs in my car to keep mice away?

No. Placing mothballs in vehicles is on the Georgia Department of Agriculture's list of misuses. See our guide on keeping mice out of your car engine for safer steps.

Are mothballs harmful to dogs and cats?

Yes. The ASPCA says all mothballs cause stomach upset if eaten, and some types can injure the liver, kidneys, or red blood cells or cause tremors and seizures. If your pet eats one, call your veterinarian or the ASPCA's animal emergency line at (888) 426-4435.

Sources

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