Zinc Poisoning in Dogs

Key Takeaways

Zinc is commonly found in household metal objects, as well as in batteries, vitamin supplements, paints, and certain ointments (e.g. sunscreen and diaper rash cream). 

• The exact mechanism of zinc toxicosis is unknown, but ingestion of a toxic dose leads to gastrointestinal upset and red blood cell destruction

• Symptoms of zinc toxicosis include appetite loss, vomiting, diarrhea, lethargy, and collapse

• Ingested metal objects show up readily on x-rays, and blood and urine tests may suggest zinc toxicosis

• Treatment involves removing the source of zinc from the digestive tract, and supportive care such as IV fluids, antiemetics, blood transfusions, and oxygen

• Prognosis depends largely on the dose ingested relative to body size and how quickly the source of zinc is removed from the GI tract

Severe hemolysis can lead to permanent organ damage or death

A Closer Look: What is Zinc Poisoning in Dogs?

In the United States, the most common cause of zinc poisoning in dogs is the ingestion of pennies. Pennies minted after 1982 are made primarily out of zinc. One post-1982 US penny contains enough zinc to be lethal to dogs weighing up to 50 pounds (23kg).

Zinc ingestion is life-threatening. If ingestion of a zinc-containing object is suspected, even if the animal is not showing symptoms, immediate medical attention is warranted. Early treatment is crucial for preventing serious symptoms, organ damage,  and death.

Risk Factors

The severity of zinc poisoning can vary in accordance with a number of factors:

Timing of treatment: with early treatment, most dogs do not develop long-term issues. If the object is removed prior to the onset of organ damage, the majority of animals recover within three days. If treatment is delayed, organ damage may become permanent or even lead to death. 

Type of object ingested: some sources of zinc are more likely to cause severe damage as they are more rapidly absorbed than others. Zinc-containing ointments generally only cause mild symptoms, while pennies can cause irreversible organ damage. 

Quantity ingested: the minimum amount of zinc required to cause poisoning depends on the dog’s size

Possible Causes

Zinc toxicosis is caused by the ingestion of zinc-containing objects. A number of common household objects contain zinc:

• Pennies: in the United States pennies are the most common cause of zinc poisoning • Batteries  • Diaper rash cream 

• Some types of vitamins and supplements • Fertilizers • Zippers • Screws and nails • Paints • Shampoo 

• Sunscreen

The exact mechanism for zinc toxicosis is not known, but it causes gastrointestinal upset and red blood cell damage (hemolysis). Zinc-containing objects also tend to adhere to the lining of the digestive tract instead of passing quickly through. This delay in transit allows for longer digestion and greater absorption of zinc from swallowed metal objects.

Main Symptoms

Common symptoms of zinc toxicosis include:

Vomiting • Decreased appetite • Diarrhea • Lethargy  • Blood in urine • Seizures • Yellow gums

Testing and Diagnosis

If ingestion of zinc-containing objects or substances is witnessed, the diagnosis is self-evident. Ingestion may occur without a witness but can leave evidence. Zinc and other metals are easily identified on x-rays, so diagnostic imaging is a useful tool when zinc ingestion is suspected.    A dog showing the symptoms associated with zinc toxicosis typically undergoes the  following diagnostics: 

• Physical exam • Blood tests • Urinalysis • Complete blood count • Diagnostic imaging 

• Specific laboratory tests that measure zinc levels in the blood

Steps to Recovery

Early treatment is focused on supportive care. Typical treatment for zinc poisoning includes: 

• IV fluids • Blood transfusion • Surgery to remove the object

• Antacids: antacids are administered every 2 to 4 hours until the zinc-containing object is removed 

• Induction of vomiting if the object is small and in the stomach Note: induction of vomiting should only be performed by a veterinary professional. There is no safe way to induce vomiting at home

• Endoscopy 

After treatment, the animal’s condition should be monitored every 24 hours until stabilized. 

The prognosis for zinc poisoning varies greatly and is influenced by the type and quantity of the object ingested, and by the timing of treatment. If the animal receives early medical attention and the object is removed prior to the onset of organ damage, most animals are able to recover within three days. If treatment is delayed or the poisoning is left untreated, permanent organ damage can develop and lead to death.

Prevention

Zinc poisoning is completely preventable by removing access to zinc-containing objects or substances. Strategies include:

• Diligent storage of zinc-containing objects 

• The purchase of zinc free products if possible

Is Zinc Poisoning Common in Dogs?

Zinc poisoning is more common in dogs than in other pets as they are often indiscriminate eaters. The Animal Poison Control Center reports over 4,000 annual cases of zinc poisoning in the United States.

Typical Treatment

• Emesis induction • Endoscopy • Surgery • IV fluids • Blood transfusion • Antacids

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