Zinc is an essential trace element that is found naturally in meat, nuts, and a few other foods. It plays a vital role in immune system functioning, wound healing, cell growth, and many other processes within the body, whether dog, human, cat, bird, or another animal. Zinc is also commonly added to many health and household products, such as supplements, coins, and sunscreen.
But while zinc is essential for a healthy body, too much can be toxic. Zinc poisoning in dogs is an unfortunately common occurrence, due to the tendency of most dogs to eat various objects they find on the ground. The results of a zinc overdose vary depending on the amount consumed, the type of zinc, and the size of the dog, but typically, the first symptoms are gastrointestinal upset, including vomiting and diarrhea. These symptoms can appear within minutes to hours of zinc consumption.
If left untreated, significant zinc poisoning can lead to the breakdown of red blood cells and eventually the death of the dog. If you suspect your dog has consumed an object or supplement containing zinc, it is crucial to get it to your veterinarian as soon as possible.
What Is Zinc Poisoning?
Zinc poisoning refers to toxicity related to the consumption of zinc products. Once swallowed, zinc breaks down in the stomach, releasing caustic zinc salts which can irritate or even break down the stomach walls.
While a dog can develop toxicity from consuming any zinc-containing product, one of the most common causes of zinc poisoning in dogs is ingesting the USA Lincoln penny. Pennies minted after 1982 are 97.5 percent zinc. A small dog potentially can be poisoned by eating just one penny.
Zinc is also found in a variety of other household products such as:
- Metal nuts, bolts, board game pieces, zippers, staples, toys, and jewelry
- Skin creams including diaper rash cream and sunscreens, shampoos, and deodorants
- Vitamins and over-the-counter cold remedies and lozenges
Symptoms of Zinc Poisoning in Dogs
Symptoms of zinc poisoning may occur very quickly after ingestion, but in some cases, symptoms may not appear until a few days later. Symptoms are also dependent upon the amount and type of zinc consumed relative to your dog's body weight.
Certain forms of zinc tend to cause more serious symptoms than others. For instance, ingestion of a zinc oxide cream may only cause stomach upset, whereas ingestion of metallic zinc can cause life-threatening toxicity.
Because zinc causes gastrointestinal irritation, the first symptoms of zinc poisoning are normally GI system issues, including vomiting and diarrhea.
Initially, your dog may have a stomach upset resulting in vomiting, diarrhea, lack of appetite, and stools that have a black tarry appearance. Your pet might also become less active, dehydrated, and lethargic.
At higher doses or for longer exposures, your dog's skin, eyes, and gums may appear yellow. This is called jaundice and is due to the breakdown of red blood cells releasing a high concentration of bilirubin into the bloodstream. The dog's stools and urine may be orange or have an orange tint as well. These symptoms indicate a progression of zinc poisoning beyond the GI tract.
If the zinc poisoning is not treated, it can progress to life-threatening anemia (a condition in which the blood doesn't have enough healthy red blood cells), seizures, kidney and liver damage, heart problems, and death.
Causes of Zinc Poisoning
Generally, a dog that consumes a topical zinc product, such as sunscreen, will not become as sick as a dog that consumes a penny or other zinc-containing metallic object. This is particularly true with small dogs, as it is likelier for the penny or other object to become stuck in the stomach for longer lengths of time.
Once in the animal's stomach, zinc reacts with stomach acids to release zinc salts, which are very caustic. These salts irritate and inflame the lining of the stomach, and can actually cause ulcerations of the stomach lining. The damage might not progress beyond this stage in dogs that ate a zinc oxide sunscreen or other topical product, but the extent of the poisoning depends on the size of your dog and the amount of zinc it consumed.
For dogs that swallowed pennies or other metallic objects, the symptoms can progress more slowly but can become far more severe. Within a few days of eating the zinc, the dog can begin to experience the breakdown of red blood cells, causing anemia. As the poisoning progresses, the dog's liver and kidneys can fail, it can develop pancreatitis, or it can develop life-threatening blood clots throughout its bloodstream.
Diagnosing Zinc Poisoning in Dogs
If you saw your pet swallow a penny or suspect your dog consumed some form of zinc, the diagnosis of zinc poisoning is quite straightforward. If not, your veterinarian will start by obtaining a history and performing a physical exam of your pet. An exam will often reveal pale mucous membranes, rapid heart rate, dehydration, jaundice, and abdominal pain.
Your veterinarian will obtain blood and urine samples to run routine laboratory tests, including complete blood count, chemistry, electrolytes, and urinalysis. These tests will indicate how your dog’s internal organs are functioning, as well as check for dehydration, assess blood zinc concentrations, check for anemia, and reveal other abnormalities consistent with zinc poisoning, including liver or kidney damage. Your vet may also take X-rays to see if a metal object can be identified in the dog's stomach or intestines.
As with any toxicity, early treatment and diagnosis are crucial. For dogs that merely ate a small amount of zinc oxide sunscreen or a similar substance, all that might be required is anti-nausea, antacids, and anti-diarrhea medications, along with subcutaneous fluids until the zinc is flushed from the dog's system. However, dogs that swallowed a zinc metallic object or consumed a large amount of zinc may need further care.
If the metal object is still within the dog's stomach or intestines, the vet will usually need to perform an endoscopy (passing a small scope with a clamping tip into the dog's digestive tract) or perform surgery to retrieve the zinc object. Once the zinc object is removed, your dog will receive intravenous fluids, as well as medications that bind to the zinc in the bloodstream and flush it out. The dog will also receive supportive medications to relieve nausea and diarrhea. Some dogs require blood transfusions if the poisoning has caused severe anemia.
Dogs that have developed kidney or liver failure, seizures, or very severe anemia will need to remain hospitalized so the veterinarian can monitor their condition while treating these serious conditions.
Prognosis for Dogs With Zinc Poisoning
Unfortunately, many people don't realize their dog has consumed zinc and ignore initially mild and general symptoms such as vomiting or diarrhea. If the dog consumed a significant amount of zinc or is a toy or small-breed dog, zinc poisoning can quickly progress to life-threatening kidney and liver failure. If this happens, your dog's prognosis becomes poor. However, with prompt treatment, most dogs will recover entirely from zinc poisoning.
How to Prevent Zinc Poisoning
Because dogs can quickly snap up items they find on the ground, it can be difficult to entirely prevent your pet from ingesting a penny or other zinc-containing item. But keeping coins safely away from your dog's reach, as well as putting zinc oxide sunscreens, zinc-containing supplements, and any small metal objects in safe locations will greatly cut down on the chances of your pet getting into life-threatening trouble.
Zinc Toxicosis in Animals. Merck Veterinary Manual.
Zinc Poisoning in Pets. VCA Animal Hospitals.