As a veterinarian, mothballs sit near the top of my list of household items I wish people understood better. They look small and harmless, almost like a candy or a toy to a curious cat, but they are concentrated pesticides in solid form. Over the years I have treated cats that batted a stray mothball across the floor and then licked their paws, and the outcomes can be frightening. This is one product where I do not soften my language at all.

I want to be completely direct with you. Mothballs are genuinely toxic to cats, and there is no safe amount to assume your cat ingested. The chemicals they release, naphthalene or paradichlorobenzene, are designed to kill insects through fumes, and a cat’s small body and limited detox pathways make it highly vulnerable. Below I explain exactly why they are dangerous, the poisoning signs, and the emergency steps that can save your cat’s life.

A cat (illustrative).

Why Mothballs Is Dangerous for Cats

Mothballs work by slowly turning from solid into gas, releasing pesticide fumes that kill moths and larvae. That same property makes them dangerous to cats, because the chemical is both inhaled and, far worse, swallowed if a cat chews or eats one. The two common active ingredients are naphthalene and paradichlorobenzene. Naphthalene is the older and more toxic of the two. Once inside a cat, these chemicals can damage red blood cells, the liver, and the kidneys, and can trigger seizures. Cats are particularly sensitive to red blood cell damage, which is why naphthalene can cause methemoglobinemia, a condition that robs the blood of its ability to carry oxygen.

🔴 The Core Risk
Mothballs are concentrated pesticides. Ingestion can cause vomiting, tremors, seizures, liver and kidney damage, and methemoglobinemia, where the blood cannot carry oxygen and the gums turn brown. Even one swallowed mothball is a medical emergency. Naphthalene mothballs are about twice as toxic as the paradichlorobenzene type, but both are dangerous.

Symptoms of Mothballs Poisoning in Cats

Signs can develop quickly after ingestion and may worsen over hours as the chemical affects the blood and organs. If you see any of these and suspect mothball exposure, treat it as an emergency.

🤮
Vomiting
Often the first sign, sometimes with a chemical smell on the breath.
😵‍💫
Tremors and Seizures
Muscle twitching, stumbling, or full seizures from neurologic toxicity.
🫁
Brown Gums
Muddy or brownish gums signal methemoglobinemia, an oxygen emergency.
😴
Weakness
Lethargy, collapse, or unwillingness to move.
🟡
Jaundice
Yellowing of the eyes or gums from liver and red cell damage.
💧
Dark Urine
Brown or red-tinged urine from red blood cell breakdown.
⚠️ Do Not Wait
Mothball poisoning can escalate fast. Brown gums, seizures, or collapse mean your cat needs emergency care now. Do not try to manage this at home or wait to see if symptoms improve.

Poisoning Timeline

This is a general picture of how mothball poisoning can unfold in a cat. The exact timing depends on how much was eaten and which chemical it contained.

🤮
0 to 2 hours
Stomach Upset
Vomiting, drooling, and a chemical odor on the breath as the body reacts.
😵‍💫
2 to 6 hours
Neurologic Signs
Tremors, restlessness, or wobbliness as the chemical reaches the nervous system.
🫁
6 to 24 hours
Blood Damage
Brown gums, weakness, and rapid breathing from methemoglobinemia and red cell breakdown.
🟡
1 to 3 days
Organ Effects
Jaundice and signs of liver and kidney damage can appear and worsen.

How Much Is Dangerous

There is no safe quantity to assume. Because cats are small and cannot detoxify these chemicals well, even a fraction of a mothball can be harmful. The figures below give rough context, not a green light for any amount.

Toxic Reference

1
mothball
A single naphthalene mothball can cause serious poisoning in a cat
2x
toxicity
Naphthalene is about twice as toxic as paradichlorobenzene
Any
ingestion
Treat any swallowed mothball as an emergency, regardless of size

The honest message is simple. Do not try to calculate whether your cat ate “enough.” If a mothball is missing or chewed, assume exposure and seek help immediately.

Common Sources of Mothballs

Mothballs and the same chemicals can turn up in more places than the closet. Here is where cats commonly encounter them.

Storage Areas

  • Closets and wardrobes
  • Stored seasonal clothing and blankets
  • Cedar chests and storage trunks
  • Attics and basements

Pest Products

  • Moth crystals and flakes
  • Moth repellent cakes
  • Some toilet and urinal deodorizer blocks
  • Garden and pest deterrent products

Outdoor and Misc

  • Mothballs used to repel rodents or snakes (misuse)
  • Sheds and garages
  • Old furniture and rugs in storage
  • Loose balls dropped on the floor

What to Do If Your Cat Ate Mothballs

Mothball ingestion is a true emergency. Act fast and do not waste time on home remedies.

1

Remove the source

Take away any remaining mothballs and get your cat away from the area. Note which type you have if the packaging is available.

2

Do not induce vomiting

Never try to make your cat vomit at home. The wrong approach can worsen the poisoning. Leave that decision to professionals.

3

Call immediately

Contact your vet or the ASPCA Animal Poison Control Center at 888-426-4435 right away. Have the product label ready to identify the chemical.

4

Go to the clinic

Mothball poisoning needs in-clinic care. Your vet may use decontamination, IV fluids, and treatment for methemoglobinemia and organ support.

5

Bring the packaging

Take the mothball container or a sample with you so the team knows whether it is naphthalene or paradichlorobenzene.

Prevention Checklist

Preventing exposure is far easier than treating poisoning. These habits keep mothballs and cats apart.

  • ✅ Avoid mothballs entirely in any home with a cat
  • ✅ Use cedar blocks or lavender sachets to protect clothing instead
  • ✅ Store fabrics in airtight containers your cat cannot open
  • ✅ Never scatter mothballs outdoors to repel pests
  • ✅ Keep cats out of closets, attics, and storage rooms with mothballs
  • ✅ Pick up any stray or dropped mothballs immediately
  • ✅ Ventilate and air out spaces that smell of mothballs
  • ✅ Keep the ASPCA poison control number saved in your phone

Safety note: Any mothball ingestion in a cat is a medical emergency. Do not induce vomiting at home. Call your veterinarian or the ASPCA Animal Poison Control Center at 888-426-4435 immediately and bring the packaging with you.