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Mothball Poisoning in Dogs

By Renee Schmid, DVM & Ahna Brutlag, DVM, MS, DABT, DABVT Pet Poison Helpline; Charlotte Flint, DVM

Care & Wellness, Medical Conditions, Pet Services

What are mothballs and how are they used?

Mothballs are solid pesticides that slowly release a vapor to kill and repel moths, their larvae, and other insects from stored clothing and fabric. Mothballs are sometimes used to repel snakes, mice, and other animals. Using mothballs in this way is not recommended and can be harmful to pets, children, and the environment.

Moth repellant products come in a variety of forms, including balls, cubes, spheres, cakes, scales, powder, and flakes. They may contain the insecticides naphthalene, paradichlorobenzene (PDB), or, rarely, camphor. Older mothballs usually contain naphthalene and the packaging often states “old fashioned mothballs.” Most modern mothballs now contain PDB instead because of concern for naphthalene’s flammability and toxicity. Camphor mothballs are more commonly found in Asia but are available for purchase in North America.

Mothballs are designed to be used in a sealed container to limit the spread of the vapors. When used and stored properly, they are relatively safe to have in a home with pets. Mothball ingestions make up a small percentage of calls to Pet Poison Helpline, a 24/7 animal poison control center. Approximately half of mothball calls are related to ingestion of naphthalene type mothballs. The remaining calls regarding mothball exposures are divided between PDB and unknown types of mothballs.

Why are mothballs toxic to dogs?

Mothballs contain a high concentration of insect repellent. Poisoning most commonly occurs when dogs ingest mothballs. Cats are more sensitive to their toxic effects, but dogs are more likely to ingest mothballs due to their curious nature. Long-term exposure to mothball fumes can harm pets and people.

“Old-fashioned” naphthalene mothballs are considered the most toxic type of mothball due to smaller amounts causing poisoning. Ingestion of naphthalene mothballs can cause gastrointestinal upset and less frequently, anemia, neurologic signs, and kidney or liver damage.

Modern PDB mothballs are less toxic but can still cause illness, especially when ingested. Ingestion of PDB mothballs commonly results in gastrointestinal upset, neurologic signs, and rarely, kidney or liver damage.

Mothballs containing camphor, an essential oil, have a low risk of poisoning with stomach upset being the most common sign. Large ingestions, however, can result in stimulation of the nervous system and possible seizures.

How many mothballs could be toxic to a dog?

As little as one mothball could poison a dog. The toxic dose depends on the size of your pet, the size of mothball, the type of mothball, and whether the mothball was ingested, or if the pet was only exposed to the fumes.

What should I do if my dog eats a mothball?

If you think your dog has eaten a mothball, contact your veterinarian or Pet Poison Helpline* (800-213-6680) right away. The sooner you seek treatment, the better the chance your dog has of fully recovering.

Do not induce vomiting or give anything orally to your dog unless your veterinarian specifically directs you to do so. When possible, put the mothball package and remaining loose mothballs into a sealed plastic bag and take them with you to the veterinary clinic for identification.

What are the clinical signs of mothball poisoning?

Mothballs dissolve slowly when ingested by dogs, and poisoning can be delayed for several days. Signs of poisoning may include:

  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Mothball-scented breath
  • Pale or brown gums
  • Weakness or lethargy
  • Labored or rapid breathing
  • Walking off balance
  • Tremors
  • Seizures

In severe cases, the dog may develop damage to the liver or kidneys. Signs of kidney damage may include vomiting, lack of appetite, increased or decreased drinking, increased or decreased urination, and foul-smelling breath. Dogs with liver damage may have decreased appetite, lethargy, vomiting, diarrhea, discoloration of the stool, dark urine, yellow discoloration of the eyes or skin (icterus), and an increased chance of bleeding.

Is there an antidote for mothball toxicity?

There is no antidote for mothball poisoning. However, when early decontamination and supportive care are provided, most dogs survive this type of poisoning.

How is mothball poisoning treated?

Early decontamination and treatment decrease the risk for serious poisoning.

If your dog has just eaten a mothball but has not yet developed any signs of poisoning, your veterinarian may induce vomiting to remove the mothball from the stomach. The veterinarian may also recommend administering activated charcoal to decrease absorption of chemicals by the gastrointestinal tract. Activated charcoal should only be administered by a veterinarian. Otherwise, aspiration into the lungs and life-threatening changes in sodium levels may occur.

If clinical signs have developed, your veterinarian will treat your pet based on the symptoms. He or she may:

  • Perform blood work to determine whether your dog has anemia or damage to the liver and kidneys.
  • Administer intravenous fluids to protect the kidneys.
  • Give anti-vomiting medication, anti-seizure medication, or medication to protect the liver. 
  • Take radiographs (x-rays), which can sometimes show whether any mothballs are present in the stomach or intestines.
  • Perform a blood transfusion in severe cases.
  • Continue to monitor follow-up blood work to ensure that your dog’s red blood cell count, liver and kidney function remain or return to normal.

What is the prognosis for recovery from mothball poisoning?

The outcome depends on many factors including the initial health of the pet, amount ingested, and time to treatment. With early treatment, pets are less likely to develop long term effects. Some pets may have permanent liver or kidney damage. Although uncommon, death may occur with high doses or when treatment is delayed.

How can I prevent mothball poisoning?

Always store mothballs out of reach of children and pets. Only store mothballs in closed, airtight containers to prevent accidental ingestion by pets. Make sure you follow label instructions, and never use mothballs loose in your home, yard, or garden to repel pests. Do not mix different types of mothballs or mix mothballs with other chemicals or insecticides. Many nonchemical methods for preventing insect damage to fabrics are available and are safer alternatives to mothballs if you have pets.

If your dog consumes mothballs, contact your veterinarian or an emergency clinic immediately, and get your pet prompt treatment. As with any poisoning, your pet has the best chance of recovery when treated as quickly as possible.

Pet Poison Helpline, an animal poison control center based out of Minneapolis, MN is available 24/7 for pet owners and veterinary professionals that require assistance treating a potentially poisoned pet. The staff provides treatment advice for poisoning cases of all species, including dogs, cats, birds, small mammals, large animals and exotic species. As the most cost-effective option for animal poison control care, Pet Poison Helpline’s fee of $65 per incident includes follow-up consultations for the duration of the poison case. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at www.petpoisonhelpline.com

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