Dr. Catherine Angle, MPH
Staff Veterinarian
Pet Poison Helpline®

In most dried food items, medications and even shoeboxes there is a little packet placed there by the manufacturer to maintain freshness.  The purpose of these little packets is to either reduce moisture in the packaging or to absorb oxygen.  Chewing up these little forgotten items is a ‘common pastime’ for canines.  Fortunately, most are harmless and require minimal or no veterinary care.  However, one is a potential problem.

Silica Gel

Q: Is it toxic?
A: Virtually non-toxic.

Q: What is it?
A: Silica is a hard porous gel that is made synthetically and utilized because of its high affinity for water.  It is placed in products to control the humidity and prevent degradation. Silica gel packets are usually 1 x 2 inches and contain multiple small white, clear or opaque beads inside.

Q: Why is it labeled “do not eat”?
A: Silica gel is not intended for consumption and therefor receives the label “do not eat”.  The dust from the processing and creation of silica is irritating to the skin, respiratory tract and gastrointestinal tract.  In people who are chronically exposed to/inhaling silica, such as a employee in a mine or factory, a progressive debilitating disease called silicosis can develop. Fortunately, silica dust is rarely encountered by our furry friends.  Some silica products are mixed with a moisture indicator, these indicators may be toxic in large doses.  If a dye is present, the silica gel will no longer be a clear to white but instead bright orange, blue, pink or green.

Q: Is it a threat to dogs?
A: No true toxicity risk exists from exposure to silica gel packets. The beads do not enlarge in the stomach and the exterior packaging is usually soft and presents little risk of injury of obstruction.

Charcoal or Activated Carbon

Q: Is it toxic?
A: Virtually non-toxic.

Q: What is it?
A: A specific type of prepared charcoal (similar to activated charcoal used in veterinary hospitals) is found in white plastic cylinders inside bags of prepared foodstuffs like dog treats, chews and jerky. If broken open the small black granules are visible. These granules are not magnetic (as compared to iron).

Q: Why is it labeled “do not eat”?
A: The charcoal is not intended to be consumed and therefor labeled “do not eat”.

Q: Is it a threat to dogs?
A: The cylinder can cause a foreign body obstruction in small dogs and can damage the oral cavity when chewed.  However, no true toxicity risk exists from the charcoal or external canister. In case you were hoping to save some money by saving the charcoal in these canisters for use in the clinic, think again. You’d need to administer the contents of thousands of canisters before achieving any therapeutic benefit! Best to stick with good old activated charcoal.

Iron

Q: Is it toxic?
A: Potentially toxic!

Q: What is it?
A: Elemental iron granules are placed in small packets called oxygen absorbers  are added to bags of pre-prepared or dehydrated food stuffs to absorb excess oxygen. This prevents oxidization (rancidity) of the food and preserves freshness ¹. Oxygen absorber packets are typically about 1×1” in size and are often found in packages of beef jerky, pepperoni, dried fruits, dog jerky treats, etc. If the oxygen absorber is broken open, dark brown to rust colored material is visible.  This material is magnetic which allows for quick differentiation between packets containing iron and those containing silica gel or charcoal.

Q: Why is it labeled “do not eat”?
A: Elemental iron can cause severe poisoning, even in the small amounts contained in one oxygen absorber packet.²  It is very irritating to the GI tract and has direct corrosive effects.  After ingestion, vomiting (with or without blood) is one of the first signs of poisoning.  In fact, vomiting is such a common finding that if a dog does not vomit, it’s probable that a toxic dose was not ingested. If the dose is large enough to cause poisoning, severe metabolic acidosis, shock and hepatic toxicity can develop 1 -5 days after the exposure. At Pet Poison Helpline®, the most severe cases of iron poisoning from oxygen absorbers have occurred in small dogs (<15 pounds). Unless a large dog ingested several oxygen absorbers or ingested unusually large ones, poisoning is much less likely.

Case management

• Owner history

Most owners will call to report that their dog ingested the packet inside of a container.  First ask how much was ingested and if there is any left.  If there is, see if the packet is labeled, what color the contents are and if the contents can be picked up with a magnet.  If it was ingested whole the owner should be asked if there is another package in the home so a duplicate of the product can be evaluated.

• Triage

If the product is labeled “silica” or if the contents of the package are white/clear beads, the owner can monitor at home and no treatments are needed.  If the contents are dark in color the owner should place a magnet over the black powder, if it isn’t magnetic, the product is likely non-toxic charcoal and, again, the owner can monitor at home.  If the owner does not have a magnet, the powder is magnetic or the product was swallowed whole, it should be assumed that iron may have been ingested and further action is needed.  If the dog weighs less than 15 pounds, the risk for poisoning is increased compared to large dogs. If at-home decontamination is appropriate, the pet owner may induce vomiting with hydrogen peroxide and then give 1-3 teaspoons of aluminum or magnesium hydroxide (Alternagel or Milk of Magnesia) to reduce the systemic absorption of iron. Alternatively, a quick call to Pet Poison Helpline® can readily help determine the pet’s risk and need for decontamination. Following emesis, the pet owner should attempt to identify the contents of the packet or bring the pet and the remaining product, the emesis, or a duplicate of the product, if available, to the clinic.

• Diagnosis

The first goal is to determine if the ingested material contains iron.  If a duplicate is available there are two characteristics of iron that can help – it is magnetic and it will appear on a radiograph as a metal density.  If the entire product was ingested consider taking a radiograph to look for metal dense object in the stomach.  Exposure can also be confirmed with a serum iron level taken 4-6 hours post ingestion. This lab test can often be run quickly and inexpensively at a local human hospital.

• Treatment
  • Depending on the amount of iron ingested and the size of the dog, additional decontamination may be needed. Following the induction of emesis, gastric lavage or whole bowel irrigation may be necessary.  Administration of oral aluminum or magnesium hydroxide (Alternagel or Milk of Magnesia) may prevent some systemic absorption of iron by precipitating elemental iron into an insoluble form.  Activated charcoal is not of benefit as it does not readily bind to iron and should not be given.
  • The pet should be given supportive care until the serum iron level results are returned. If clinical signs of gastrointestinal upset are seen anti-emetics, H₂ blockers such as famotidine, sucralfate and IV fluids may be needed. 
  • If the iron level comes back greater then 300-400 mcg/dL chelation therapy with deferoxamine may be necessary to prevent organ damage³.

References

1. Byun et al. Oxygen scavenging system containing a natural free radical scavenger and a transition metal, Food Chemistry 124(2011) 615-619. <Where should this reference be placed in the text?
2. Brutlag et al. Iron Intoxication in a Dog Consequent to the Ingestion of Oxygen Absorber Sachets in Pet Treat Packaging, J. Med. Toxicol. Vol 5, num 3, Sept. 2009  <Where should this reference be placed in the text?
3. Griffith et al. Effect of Deferasirox on Iron Absorption in a Randomized, Placebo-Controlled, Crossover Study in a Human Model of Acute Supratherapeutic Iron Ingestion. Annals of Emergency Medicine, Volume xx, no. x: Month 2011.