Mothballs may deter cats with their strong smell, but they pose serious health risks to cats, other animals, children, and the environment. Using them outdoors as an animal repellent is also illegal in the United States. There are safer, more effective ways to keep cats out of your yard or garden.
Why Mothballs Are a Bad Choice
Mothballs work by releasing toxic vapors designed to kill clothes moths in enclosed spaces like storage containers and garment bags. That’s their only legal use. The EPA regulates mothballs as pesticides, and the label on every package specifies exactly where and how they can be used. Scattering them in your garden, under a porch, or around flower beds to repel cats, snakes, or rodents violates federal pesticide law.
Beyond the legal issue, mothballs placed outdoors contaminate soil, plants, and water. They dissolve in rain, and the chemicals leach into the ground where they can affect anything living nearby.
How Mothballs Can Poison Cats
Cats are more sensitive to mothball chemicals than dogs or most other animals. As little as one mothball can poison a cat. The three active ingredients found in mothballs, in order of toxicity, are camphor, naphthalene, and paradichlorobenzene (PDB). Older naphthalene mothballs are the most commonly encountered dangerous type.
Poisoning most often happens when a cat eats a mothball, but it doesn’t have to. Cats can absorb the chemicals through their skin or by breathing the fumes over time. Long-term exposure to mothball vapors harms both pets and people. A cat walking through a garden where mothballs are scattered could pick up residue on its paws, then ingest it while grooming.
Signs of mothball poisoning in cats include vomiting, diarrhea, abdominal pain, weakness, and lethargy. More serious cases can cause pale or brown gums (a sign of anemia or oxygen problems in the blood), labored breathing, loss of coordination, tremors, seizures, and liver or kidney damage. You may also notice a distinct mothball smell on the cat’s breath.
Safer Ways to Keep Cats Out of Your Yard
Several alternatives actually work well without putting any animal at risk.
Motion-activated sprinklers use an infrared sensor to detect movement and release a short burst of water. Most models cover an area of about 35 by 45 feet and can fire up to 1,000 times on a single battery. Cats hate the surprise, and they learn to avoid the area quickly.
Ultrasonic deterrents emit a high-pitched sound triggered by a motion sensor. The frequency is too high for humans to hear but startles cats. Solar-powered versions require almost no maintenance once placed.
Physical barriers are simple and effective. Scat mats, which are flexible plastic sheets with small spikes, discourage cats from walking or digging in a specific spot. You can also place pinecones, lava rocks, large river stones, or poultry fencing over garden beds. Pushing chopsticks into the soil of potted plants works for smaller areas.
Scent-based repellents take advantage of smells cats naturally dislike. Citrus peels, coffee grounds, vinegar, eucalyptus, citronella, garlic, and dried rue are all options. You can also plant rue directly in your garden as a living deterrent. The downside is that scents fade, so you’ll need to reapply them regularly, especially after rain.
Blocking shelter access addresses why cats come around in the first place. Cats look for dry, warm spots away from the elements. Sealing off crawl spaces, gaps under decks, or openings in sheds removes the invitation. Just make sure no cats are already inside before you close things up.
If a Cat Has Been Exposed to Mothballs
If you suspect a cat has eaten a mothball or been exposed to mothball fumes for an extended period, get the cat to a veterinarian as soon as possible. Bring the mothball packaging if you have it, since treatment depends on which chemical is involved. Don’t wait for symptoms to appear. With naphthalene especially, early treatment matters because the damage to red blood cells and organs can progress rapidly once it starts.