Toxicosis From Mothballs in Animals

The term "mothballs" generally refers to moth-repellent spheres; however, moth repellents can also be sold as flakes, crystals, cakes, and other forms.

In addition to being a key ingredient of mothballs, naphthalene is most often used as an anthelmintic, insecticide, and insect repellent. However, it has also been used as an antiseptic, expectorant, and treatment for oral and dermal diseases. PDB is most often found in deodorizers. Camphor is an essential oil that is used most often as a fragrance; however, it can also be used as a food additive and as a topical analgesic.

Camphor is considered the most toxic of the mothball active ingredients, followed by naphthalene, then PDB. Ingestion is the most common type of exposure, but inhalation and transdermal absorption can also result in toxicosis.

Naphthalene is a GI tract irritant, so exposure almost always causes GI signs such as vomiting and anorexia before progressing to systemic signs. With large exposures, hemolytic anemia, methemoglobinemia, dyspnea, and pale gums can occur. In addition, neurological changes such as trembling, tremors, ataxia, and seizures are noted in rare cases.

PDB exposure primarily causes abdominal pain, vomiting, lethargy, and trembling. Large doses or chronic repeated ingestion can lead to weakness, ataxia, and muscle tremors. In addition, liver and kidney changes can occur. Although blood abnormalities are not noted with acute exposure, anemia has been reported with chronic exposure.

Camphor exposure primarily causes CNS depression, altered mentation, CNS excitation, and seizures; it can also result in GI upset.

Mothball types can be differentiated by a float test, as follows:

• Drop the mothball in room temperature water:

  • If it floats, the mothball is camphor.

  • If it sinks, the mothball is either naphthalene or PDB.

• Drop the naphthalene/PDB mothball into a saturated salt solution (125 mL [4 ounces] of tepid water into which 45 g [3 tablespoons] of regular salt has been dissolved):

  • If it floats, the mothball is naphthalene.

  • If it sinks, the mothball is PDB.

After mothballs have been ingested, diagnosis of toxicosis is more difficult.

Radiography can be helpful to differentiate naphthalene mothballs from PDB mothballs. PDB mothballs are densely radiopaque; naphthalene mothballs are radiolucent or faintly radiopaque.

Decontamination is the most important measure to prevent mothball toxicosis. Decontamination consists of inducing emesis (vomiting) and then administering an antiemetic to stop vomiting, followed by a single dose of activated charcoal with a cathartic. Because mothballs dissolve very slowly, decontamination can still be performed after an appreciable amount of time has passed since ingestion.

In mothball-exposed animals without clinical signs, emesis can be induced up to 4 hours after exposure. If emesis is unproductive and the exposure is very large, gastric lavage can be considered. An antiemetic should be administered after emesis is complete.

Whether or not they have received an emetic, mothball-exposed animals should be given a single dose of activated charcoal with a cathartic (eg, sorbitol) because there is no guarantee that even with emesis, all mothballs will be removed from the animal’s GI tract. may be administered once within 24 hours of ingestion. Administration of activated charcoal can be beneficial in absorbing residual mothballs from the GI tract even after the time frame that emesis might help has passed.

If outpatient monitoring is planned, fluid therapy should be administered along with activated charcoal. Baseline laboratory work (CBC/serum biochemistry panel) should be performed, and repeated lab work might be necessary in animals that develop signs of methemoglobinemia, hemolysis, Heinz body anemia, liver enzyme elevation, or kidney changes.

Animals with clinical signs of mothball toxicosis should be treated on an inpatient basis. Fluid therapy should be started. Additional treatment is supportive. GI signs can be treated with continued antiemetics and GI protectants (sucralfate, H₂ blocker/proton pump inhibitor).

Induced emesis is contraindicated in animals exhibiting CNS signs. CNS signs can be treated with methocarbamol for tremors and standard anticonvulsants for seizures.

Ascorbic acid (vitamin C) can be used for methemoglobinemia; however, blood transfusions might be necessary if the patient has severe anemia.

Hepatoprotectants such as N-acetylcysteine (NAC) and S-adenosylmethionine (SAMe) can be considered for patients showing signs of hemolysis or liver enzyme elevations. In addition to working as a free radical scavenger to decrease oxidative damage, NAC can be helpful in maintaining glutathione and sulfate concentrations. SAMe can also help increase glutathione levels and prevent depletion.

• Cohen SL. Mothballs. In Hovda LR, Brutlag AG, Poppenga RH, Epstein SE, eds. Blackwell's Five-Minute Veterinary Consult Clinical Companion: Small Animal Toxicology. 3rd ed. Wiley Blackwell; 2024:583-589.

• Gwaltney-Brant SM. Miscellaneous indoor toxicants. In: Peterson MP, Talcott PA, eds. Small Animal Toxicology. 3rd ed. Elsevier; 2013:291-308.

• Schmid R, Brutlag A, Flint C. Mothball poisoning in dogs. VCA Animal Hospitals; 2021.

• Gwaltney-Brant S, Shell L. Mothball toxicosis. VINcyclopedia of Diseases; 2018. https://www.vin.com/Members/Associate/Associate.plx?from=GetDzInfo&DiseaseId=2692&pid=607.

• Also see pet owner content regarding household hazards.