Are Moth Balls Toxic to Dogs? Symptoms, Dangers &...

Are Moth Balls Poisonous to Dogs?

Yes. Mothballs are among the most dangerous household items a dog can encounter. Unlike some human foods that cause mild gastrointestinal upset, mothballs contain concentrated chemical pesticides designed to release toxic vapors in enclosed spaces. When a dog chews or swallows a mothball, the concentrated active ingredient is absorbed directly through the gastrointestinal tract at doses far exceeding what the body can process safely.

Mothballs are regulated by the U.S. Environmental Protection Agency (EPA) as pesticides, and their labels carry the signal word "WARNING" or "DANGER" — the two highest toxicity classifications. Dogs are at particular risk because they may find mothballs in closets, basements, attics, or storage areas and mistake the small, round pellets for treats or toys.

How Much Mothball Can Kill a Dog? Toxic Dose Thresholds

There is no safe dose of mothball ingestion for dogs. However, understanding toxic thresholds helps veterinarians assess severity and prognosis. The following data reflects published toxicological thresholds from veterinary toxicology references.

Mothball Toxic Dose Thresholds by Dog Weight

Dog Weight	Naphthalene Toxic Dose	Approx. Mothballs (standard 2.7g each)	Risk Level
10 lb / 4.5 kg	~35 mg/kg (158 mg total)	1 mothball	Potentially Lethal
25 lb / 11.3 kg	~35 mg/kg (396 mg total)	1–2 mothballs	Severe Toxicity
50 lb / 22.7 kg	~35 mg/kg (794 mg total)	2–3 mothballs	Severe Toxicity
75 lb / 34 kg	~35 mg/kg (1,190 mg total)	3–4 mothballs	High Risk
100 lb / 45.4 kg	~35 mg/kg (1,589 mg total)	4–5 mothballs	High Risk

Key takeaway: For naphthalene-based mothballs, the reported toxic dose in dogs is approximately 35 mg/kg of body weight. A single standard mothball weighs roughly 2.7 grams and contains about 99% naphthalene — meaning one mothball delivers approximately 2,673 mg of naphthalene. For a 10-pound dog, that single mothball represents a dose of roughly 594 mg/kg, which is over 17 times the toxic threshold. Even partial ingestion of one mothball by a small dog constitutes an emergency.

For paradichlorobenzene (PDB), the oral LD50 in dogs is reported at approximately 500–750 mg/kg, but clinical signs of toxicity have been observed at significantly lower doses, and individual sensitivity varies widely. Camphor is dangerous at doses as low as 50 mg/kg.

What Are the Symptoms of Mothball Poisoning in Dogs?

Mothball poisoning symptoms follow a predictable timeline, though onset speed depends on the active ingredient, the dose ingested, and the individual dog's size and health status.

Symptom Timeline After Ingestion

Timeframe	Symptoms	What's Happening
0–30 minutes	Drooling, nausea, vomiting (may smell like mothballs), pawing at mouth, lethargy	Gastrointestinal irritation; chemical burning of mucous membranes
30 min – 2 hours	Vomiting (may contain blood), diarrhea, abdominal pain, tremors, restlessness, difficulty breathing	Systemic absorption begins; red blood cell damage initiating (naphthalene); neurotoxic effects (PDB/camphor)
2–12 hours	Pale or brownish gums (methemoglobinemia), weakness, rapid heart rate, seizures (camphor/PDB), collapse	Hemolytic crisis; liver enzyme elevation; CNS depression or excitation
12–48 hours	Dark or brown urine (hemoglobinuria), jaundice (yellow gums/eyes), kidney failure, liver failure, coma	End-organ damage; Heinz body anemia; potential multi-organ failure

What Should I Do If My Dog Ate a Mothball?

Speed is critical. Follow these steps in order during the first 15 minutes after discovering ingestion.

Even if your dog seems fine, go to the vet. Mothball poisoning has a delayed onset. A dog that appears normal 30 minutes after ingestion can develop hemolytic crisis within hours. Early intervention — before symptoms become severe — dramatically improves survival rates.

How Long Does It Take for Symptoms to Appear?

Symptom onset varies by the active compound ingested:

• Camphor: Signs can appear within 5–15 minutes. Seizures have been reported within 20 minutes of ingestion. This is the fastest-acting mothball toxin.
• Naphthalene: Gastrointestinal signs (vomiting, drooling) typically appear within 30 minutes to 2 hours. Hemolytic anemia signs (pale/brown gums, dark urine) develop over 12–72 hours as red blood cells are progressively destroyed.
• Paradichlorobenzene: Initial GI signs within 1–4 hours. Neurological signs (tremors, seizures) and liver damage may not become apparent for 24–48 hours.

The delayed hemolytic phase of naphthalene poisoning is particularly dangerous because owners may believe their dog has recovered after initial vomiting stops, only for the dog to collapse 1–3 days later from severe anemia. This is why veterinary monitoring for at least 48–72 hours is recommended even after seemingly successful initial treatment.

Veterinary Treatment: What to Expect and Costs

When you arrive at the veterinary clinic, the treatment protocol will depend on the active ingredient, time since ingestion, and your dog's current clinical signs. Here is what you can expect:

Diagnostic Workup

• Complete blood count (CBC) — to assess red blood cell destruction, Heinz body formation, and anemia severity ($80–$150)
• Blood chemistry panel — to evaluate liver enzymes (ALT, AST), kidney values (BUN, creatinine), and bilirubin levels ($100–$200)
• Methemoglobin level — specific test to quantify oxygen-carrying impairment ($50–$100)
• Urinalysis — to check for hemoglobinuria (blood pigment in urine) indicating active hemolysis ($50–$80)
• Abdominal radiographs — mothballs are radiopaque and may be visible on X-ray, confirming ingestion and quantity ($150–$300)

Treatment Options

Treatment	Purpose	When Used
Gastric lavage (stomach pumping)	Remove unabsorbed mothball material	Within 2 hours of ingestion, under sedation
Activated charcoal (1–4 g/kg)	Bind remaining toxin in GI tract	After lavage or if vomiting has been controlled
IV fluid therapy	Support kidneys, maintain hydration, flush toxins	All cases; typically 24–72 hours of continuous fluids
Methylene blue (1–2 mg/kg IV)	Reverse methemoglobinemia	Naphthalene poisoning with brown gums or low SpO2
Blood transfusion	Replace destroyed red blood cells	PCV drops below 20% or clinical signs of severe anemia
N-acetylcysteine (NAC)	Liver protectant, antioxidant support	PDB ingestion or elevated liver enzymes
Anti-seizure medication (diazepam/levetiracetam)	Control neurological symptoms	Camphor or PDB poisoning with tremors/seizures

Expected Cost Range

Mothball poisoning treatment is expensive due to the intensive monitoring and potential need for blood products:

• Mild case (early presentation, small ingestion): $800–$2,000 — includes emergency exam, decontamination, IV fluids, and 24-hour monitoring
• Moderate case (hemolysis developing, requires extended care): $2,000–$5,000 — adds blood transfusion, extended IV fluids, and repeated bloodwork
• Severe case (organ damage, ICU-level care): $5,000–$10,000+ — includes multiple transfusions, liver support, dialysis consideration, and 3–5 days of hospitalization

Consult your veterinarian about your dog's specific situation. Pet insurance with emergency/illness coverage can significantly offset these costs if you have an active policy.

Will My Dog Survive Mothball Poisoning?

Prognosis depends on three factors: how much was ingested relative to body weight, how quickly veterinary treatment was initiated, and which compound was involved.

• Early treatment (within 1–2 hours of ingestion): Good to excellent prognosis. Dogs that receive gastric decontamination before significant absorption occurs often recover fully within 48–72 hours with supportive care.
• Delayed treatment (4–12 hours post-ingestion): Guarded prognosis. Hemolytic damage is underway, but aggressive treatment including transfusion and IV fluids can still result in recovery over 5–7 days. Some residual liver or kidney damage may persist.
• Late presentation (24+ hours, organ damage evident): Poor to grave prognosis. Once multi-organ failure develops — particularly acute kidney injury combined with severe hemolytic anemia — mortality rates increase significantly. According to the Merck Veterinary Manual, dogs presenting with methemoglobinemia and Heinz body anemia have a more guarded prognosis that depends on response to methylene blue therapy and transfusion support.

Dogs with G6PD deficiency (a red blood cell enzyme deficiency more common in certain breeds and lines) are at higher risk for severe hemolysis from naphthalene, similar to the condition in humans. There is no routine screening test for this in dogs, so all dogs should be treated as potentially susceptible.

Prevention: Keeping Mothballs Away From Your Dog

The only reliable prevention strategy is eliminating mothballs from any area your dog can access. Mothballs are not effective in open spaces anyway — they require airtight containers to build up the vapor concentration needed to kill moths.

Related Household Toxins to Watch For

If your home contains mothballs, it likely contains other common canine toxins. Be aware of these related hazards, which are also frequent callers to the ASPCA Animal Poison Control Center:

• Xylitol — a sugar substitute found in sugar-free gum, some peanut butters, and baked goods. Causes rapid, life-threatening hypoglycemia and liver failure in dogs at doses as low as 50 mg/kg.
• Grapes and raisins — cause acute kidney failure in dogs. The toxic mechanism was identified in 2021 as tartaric acid sensitivity, but no safe dose has been established.
• Rodenticides (rat poison) — anticoagulant baits cause internal bleeding; bromethalin-based baits cause brain swelling. Often stored in the same areas as mothballs.
• Antifreeze (ethylene glycol) — sweet-tasting liquid that causes rapid, fatal kidney failure. As little as 1–2 tablespoons can kill a medium-sized dog.
• Onions and garlic — like naphthalene, these cause oxidative damage to red blood cells (Heinz body anemia). The mechanism is similar, making dogs that have ingested mothballs potentially more vulnerable to these foods.
• Cocoa mulch — garden mulch made from cocoa bean hulls contains theobromine and is attractive to dogs. Can cause chocolate-like toxicity.

This article is intended for informational purposes only and does not replace professional veterinary advice. If you suspect your dog has ingested mothballs or any toxic substance, consult your veterinarian immediately.