Why naphthalene mothballs are toxic
Naphthalene is absorbed through the gut and lungs, then converted in the liver to reactive metabolites that destroy red blood cell membranes, causing haemolytic anaemia.
Unlike modern para-dichlorobenzene mothballs, naphthalene balls are white and visibly shrink as they sublimate into gas—even in sealed containers.
Pets find them by chewing through storage bags, dragging them from closets, or knocking over boxes where they were stored near pet food.
Cats are especially vulnerable because they lack certain liver enzymes needed to safely process naphthalene, making even small bites potentially fatal.
Why speed matters
Delaying care significantly worsens outcomes. Some signs appear hours or days later, so "looks fine right now" is not a reason to wait.
Symptoms of naphthalene-mothballs poisoning
- Red, brown, or yellowish gums that indicate haemolytic anaemia starting 1 to 3 days after exposure
- Lethargy and weakness that worsens progressively as red blood cells break down
- Loss of appetite and vomiting within the first 24 hours
- Dark red or brown urine from haemoglobin released by damaged red blood cells
- Rapid breathing and heart rate as the body struggles to deliver oxygen with fewer red blood cells
What to do right now
- Call your vet or the ASPCA Animal Poison Control Center (888-426-4435) or Pet Poison Helpline (855-764-7661) as soon as you suspect ingestion, even if no symptoms are visible yet.
- Collect any remaining mothballs and packaging to bring to the clinic—the vet needs to know whether they contain naphthalene or para-dichlorobenzene.
- Do not induce vomiting unless directed by your veterinarian; the fumes themselves can irritate the airway.
- Keep your pet quiet and minimise exertion, since physical stress increases oxygen demand in an animal already struggling with anaemia.
- Monitor urine colour and gum colour closely over the next 72 hours, as delayed anaemia is the hallmark of naphthalene poisoning.
Sources & further reading
- ASPCA Animal Poison Control — pet poison database & dosage references
- Pet Poison Helpline — toxicology triage guidelines
- Merck Veterinary Manual — toxicology monographs
- Vets Now (UK) — emergency toxicosis guidance
Other poisonings with overlapping signs
- Ammonia Cleaner Poisoning in Dogs and Cats — shares signs: red
- Cyclamen Poisoning: Symptoms and First Aid — shares signs: red
- Ice Melt Products: What Every Pet Owner Must Know — shares signs: red
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Frequently asked questions
Is Naphthalene Mothballs Poisoning in Dogs and Cats poisonous to a dog or cat?
Naphthalene is absorbed through the gut and lungs, then converted in the liver to reactive metabolites that destroy red blood cell membranes, causing haemolytic anaemia.
What are the symptoms of naphthalene-mothballs poisoning?
Red, brown, or yellowish gums that indicate haemolytic anaemia starting 1 to 3 days after exposure; Lethargy and weakness that worsens progressively as red blood cells break down; Loss of appetite and vomiting within the first 24 hours; Dark red or brown urine from haemoglobin released by damaged red blood cells
What should I do if my pet ate Naphthalene Mothballs Poisoning in Dogs and Cats?
Call your vet or the ASPCA Animal Poison Control Center (888-426-4435) or Pet Poison Helpline (855-764-7661) as soon as you suspect ingestion, even if no symptoms are visible yet. Collect any remaining mothballs and packaging to bring to the clinic—the vet needs to know whether they contain naphthalene or para-dichloro…
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