Mothballs contain naphthalene or paradichlorobenzene — both cause severe poisoning in dogs.
Even a single mothball can be life-threatening. Naphthalene is the more dangerous of the two.
Naphthalene damages red blood cells by oxidizing hemoglobin, causing hemolytic anemia and Heinz body formation. It also damages the liver and brain. Paradichlorobenzene is less potent but still causes GI signs, ataxia and tremors. Both have a long half-life in body fat.
Sources
A single naphthalene mothball can cause clinical signs in a medium dog. Symptoms can be delayed by 24–48 hours.
Contact your veterinarian or an emergency animal poison hotline immediately. Do not induce vomiting unless instructed by a vet.
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