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Ask the Vet: My Pet Ate A Handwarmer by Dr Stefanie Wong
January 24, 2018

Temperatures have been dropping and snowstorms have been bringing feet of snow to the Sierras. If you have a trip planned to Tahoe or another snowy destination handwarmers may be one of the items you pack with you. What happens if your pet manages to find their way into your bag and pulls one of these out? Let's say they chew on it or ingest all of it in one big gulp? What should you do?

First, let's talk about how hand warmers work. They are primarily made of iron – broken into tiny little pieces to form a powder. When the pouch is exposed to oxygen, it oxidizes, producing a chemical reaction that will yield heat. There are a few other additives to speed the reaction, spread it out along the entire length of the packet and trap moisture, however iron is the ingredient of interest for us.

Once the hand warmer is used, it is no longer considered toxic, as the iron is essentially considered "inactivated." However, if it is an unused packet, then it can be quite dangerous depending on the amount ingested. Iron toxicity can vary from mild to severe - at its worst it can be fatal.


At lower amounts of ingestion, iron toxicity may cause GI or stomach and intestinal upset (vomiting, diarrhea). As iron can be corrosive to the stomach lining, we can see stomach irritation to the point of causing bleeding and ulcers (vomiting blood, or having black/tarry stool). At higher amounts of ingestion, more severe side effects may be seen, such as cardiac abnormalities – fast heart rate and abnormal heart rhythms, neurologic abnormalities – tremors or seizures, and internal organ problems – kidney or liver failure.


If your pet has ingested an un-used hand warmer or parts of it, we recommend calling animal poison control immediately, or traveling to your nearest veterinary hospital.

If ingestion has been recent, the first step is to decontaminate by inducing vomiting. We can give an injection of a medication that will immediately trigger your pet to vomit and empty their stomach. This removes as much iron as we can from the stomach so it cannot continue to be absorbed into the systemic circulation.

X-rays can then be taken to visualize how much iron is left in the stomach and intestines after vomiting has taken place – iron will easily show up on an x-ray. This helps us to determine if we need to induce vomiting again. Bloodwork may be performed in order to determine baseline liver and kidney values and a blood sample can be drawn to measure serum iron levels, to determine level of toxicity and if chelation therapy is needed (treatment to bind the iron in the circulation). Milk of magnesia can be given orally to bind and inactive iron.

If large enough amounts were ingested, hospitalization is often recommended. This allows us to administer IV fluids – prevent dehydration from vomiting and diarrhea, prevent and/or treat shock and correct any existing electrolye abnormalities. We also can monitor and treat any cardiac or heart abnormalities, give stomach protectants to lower the acidity of the stomach to minimize ulcer formation and treat tremors or seizures if noted.

Typically if symptoms are going to be seen, they will be seen within 8 hours following ingestion.

Thankfully, if a low amount is ingested, your pet should make a full recovery. However, larger amounts can be quite dangerous. Always try to store handwarmers and other items containing iron (multivitamins especially prenatal vitamins, fertilizers, oxygen absorbers – packets found in beef jerky and other food bags, etc) out of reach of your pets.

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