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9 Human foods that are dangerous to dogs
- Dr. Melissa Rose MRCVS
- Oct 24, 2023
- 12 min read
Our beloved dogs are more than just pets; they are cherished members of our families. It's only natural to want to share our favourite foods with them. However, many common human foods can be incredibly harmful, even fatal, to our four-legged friends. In this article, we'll explore nine everyday items found in our kitchens that can pose significant health risks to dogs. From chocolate and grapes to xylitol and food moulds, we'll delve into the reasons behind their toxicity, how much is considered dangerous, the symptoms to watch out for, and what you should do if your dog ingests these substances. Our aim is to provide you with the knowledge needed to prevent accidental poisonings and ensure the safety and well-being of your furry companions. Remember, an ounce of prevention is worth a pound of cure, and being informed about the hazards lurking in your kitchen can make all the difference in your dog's health and happiness
Chocolate
Why/How is it Toxic?
Chocolate, as well as other foods like tea, coffee, cola drinks, and caffeine tablets, contain chemicals called methylxanthines. The toxic components in chocolate are theobromine and caffeine, with theobromine being the most dangerous. These substances can cause problems in both humans and animals. They interfere with cellular receptors in the body, leading to issues like increased heart rate, muscle contractions, and stimulation of the nervous system.
How Much is Toxic?
The toxicity of chocolate varies depending on factors like the type of chocolate and the size of the dog. Dark chocolate is more toxic, while milk chocolate is less so. For instance, a small dog can be seriously affected by eating just a small amount of cocoa powder or dark chocolate, while they would need to eat a larger quantity of milk chocolate to experience the same effects. The type of chocolate matters - baker's chocolate is highly toxic, while milk chocolate is less so.
A good resource for any pet owner is this toxic dose calculator for dogs from the emergency and critical care company Vets Now. Here you can type in your dogs weight and the amount ad type of chocolate they have eaten and find out immediately if you need to take action and call your local vet
What Symptoms Will I See?
If a dog consumes chocolate, they may show symptoms like nausea, vomiting, diarrhoea, increased thirst and urination, restlessness, heart problems, tremors, seizures, and even death in severe cases. The symptoms can range from mild, such as vomiting and diarrhoea, to severe, like seizures or heart issues. The high fat content in chocolate can also trigger pancreatitis in some animals.
What Should I Do?
If your pet eats chocolate and shows symptoms, it's essential to seek immediate veterinary care. The treatment may include inducing vomiting (if the ingestion was recent), administering activated charcoal to help absorb the toxins, and providing medication to control symptoms like seizures or heart issues. In severe cases, your pet might need intravenous fluids and monitoring to ensure their recovery. The earlier you seek help, the better the chances of a successful outcome.
Grapes and Raisins (including hot cross buns)
Why/How is it Toxic?
The exact reason why grapes can be toxic to dogs isn't fully understood. Some ideas suggest that grapes might be contaminated with harmful substances like heavy metals, pesticides, or mycotoxins. Another theory is that there could be something within the grapes themselves. However, studies looking into these possibilities haven't found any clear evidence of contamination. Interestingly, a recent case series found a potential link between grapes, cream of tartar, and tamarind toxicity. They think tartaric acid, a natural substance found in grapes in relatively high amounts, might be a common factor causing the issues in these cases. But the exact cause of grape toxicity in dogs remains a bit of a mystery.
How Much is Toxic?
At present, there isn't a clear dose-response relationship, with some dogs anecdotally being fed some form of the fruit daily and being fine whilst others can ingest only a small quantity and be severely affected. For this reason any amount of grapes, raisins, or sultanas should be considered a problem.
What Symptoms Will I See?
Symptoms of raisin poisoning usually appear within six hours of ingestion, but they can show up within 24 hours. Early signs include vomiting, diarrhoea, loss of appetite, weakness, dehydration, tremors, and lethargy. Dogs may also show increased thirst. Severe kidney failure can develop within 24 to 72 hours, and once that happens, most affected dogs don't survive. Urine and blood tests can confirm the condition, and dogs with kidney failure have a poor prognosis.
What Should I Do?
If your dog eats grapes, raisins, or sultanas, you should consider it a treatable emergency. The digestion of these fruits is slow, so decontamination within hours of ingestion can help. This can be done through a trip to your vets where they will safely induce vomiting and prescribe activated charcoal to feed to your dog afterwards. Fluid therapy through intravenous (IV) fluids might also be recommended for 24-48 hours to rehydrate and support kidney function. In severe cases with little to no urine output (anuria) the prognosis is guarded even with these measures. Early intervention is key to a better chance of recovery.
Onions
Why/How is it Toxic?
Onions, a widely used vegetable, contain chemical compounds known as sulfoxides and aliphatic sulfides. The principal toxin in onions is n-propyl disulfide, which interferes with the regeneration of a substance called reduced glutathione, needed to protect red blood cells from oxidative damage. This interference results in the precipitation of denatured haemoglobin on the surface of red blood cells, forming clumps known as Heinz bodies. These Heinz bodies trigger both intra- and extravascular haemolysis, causing the breakdown of red blood cells and ultimately leading to a condition known as haemolytic anaemia.
How Much is Toxic?
Even small amounts of onions can be problematic for pets. For dogs, ingestion of more than 0.5% of their body weight in onions at one time is a concern. Fatal effects can occur in dogs that consume a relatively high dosage, such as 600-800 grams, in a single meal or over several days.
What Symptoms Will I See?
Initially, symptoms of onion toxicity in pets might resemble gastroenteritis and include vomiting, diarrhoea, abdominal pain, loss of appetite, depression, and dehydration. Over time, as red blood cells are damaged, additional symptoms can appear: pale mucous membranes, rapid breathing, lethargy, dark-coloured urine, jaundice (yellowing of the skin and eyes), weakness, and a fast heart rate. Blood tests may show increased white blood cells, Heinz body anaemia, and methemoglobinemia.
What Should I Do?
There's no specific antidote for onion toxicity, so the focus is on supportive care. If the pet has ingested onions recently, gastric decontamination might be considered (by inducing vomiting or by gastric lavage), and adsorbents such as activated charcoal could be used. Hospitalisation can be required to administer intravenous fluids and, in severe cases, blood transfusions. Although fatal effects in dogs are rare, the best strategy is to avoid exposing your dog to onions in their food.
Garlic
Why/How is it toxic?
Garlic (Allium sativum) contains compounds like allicin and ajoene. While garlic is considered to be less toxic and therefore safer for dogs than onions, these compounds do still have the potential to affect red blood cells in dogs and horses.
How much is toxic?
In dogs, it appears that high doses of garlic are needed to induce any changes in red blood cells. One study reported doses of 1.25 ml/kg of body weight, equivalent to 5 grams of whole garlic per kilogram over several days, caused haematological abnormalities . It is unlikely that any pet dog would ingest garlic in these quantities.
What symptoms will I see?
While dogs given garlic extract showed changes in erythrocyte count, haematocrit, haemoglobin concentration, Heinz body formation, increased erythrocyte-reduced glutathione concentration, and eccentrocytes, none of the dogs developed haemolytic anaemia and therefore there would be no symptoms to see at home.
What should I do?
While garlic is less toxic than onions, it can still have adverse effects on red blood cells in dogs. It is highly unlikely your dog will ever ingest the quantity of garlic needed to cause problems. But if you are concerned then you should speak with your vet.
Avocado
Why/How is it toxic?
Avocado fruit, pits, leaves, and the entire avocado plant are potentially poisonous to various animals, including birds, horses, goats, sheep, mice and rabbits. The toxicity is primarily due to a fungicidal toxin called persin, which is found in both the fruit and leaves of the avocado tree (Persea americana). However according to the Veterinary Poisons Information Service acute ingestion of avocado in dogs and cats is not usually a concern. Of more concern is the hard central stone which, if eaten by a dog, could lead to gastrointestinal obstruction requiring emergency surgery to resolve.
How much is toxic?
The lethal dose of avocados is not well-determined. The only documented cases of avocado poisoning in dogs was published in 1994 in kenya in two dogs who were eating avocado on a long term basis.
What symptoms will I see?
Acute ingestion of avocado will likely lead to self resolving mild gastrointestinal symptoms (vomiting and diarrhoea). As outlined above the biggest danger in dogs would be eating the stone. If this were to cause a blockage in the intestines symptoms would include: vomiting, abdominal pain, lethargy, inappetance.
What should I do?
If your dog has eaten a small volume of the fruit as a one off then simply monitoring at home is all you should need to do. If they have eaten the central stone then you should speak with your local vet immediately (even if this is out of hours), if caught soon after eating then they will likely recommend inducing vomiting to bring the stone back up to ensure it does not get the chance to cause a blockage in the small intestine.
Macadamia Nuts
Why/How is it toxic?
Macadamia nuts, originating from the Macadamia integrifolia trees in the continental USA and Macadamia tetraphylla in Hawaii and Australia, pose a potential threat to dogs. They contain an unknown toxin that affects a dog's muscles, digestive system, and nervous system. Although the precise mechanism of action is still unidentified, it may involve certain constituents of the nuts, processing contaminants, or mycotoxins. These toxic compounds are believed to be unique to macadamia nuts and not found in other types of nuts.
How much is toxic?
The toxic dose of macadamia nuts in dogs varies widely, ranging from 2.4 to 62.4 grams per kilogram of body weight. This broad range implies that some dogs can become ill after ingesting a small quantity, while others may require a more substantial amount to exhibit signs of toxicity (Hansen et al., 2000).
What symptoms will I see?
When a dog consumes macadamia nuts, they may begin to exhibit a range of symptoms, which can manifest within 12 hours after ingestion. These symptoms often include weakness, hind limb paralysis, tremors, vomiting, hyperthermia, and increased heart rate. Affected dogs may also display pain when their limbs are manipulated. Although macadamia nut toxicity is usually not fatal, these symptoms can be quite distressing and uncomfortable for your pet.
What should I do?
If you suspect that your dog has ingested macadamia nuts or is displaying symptoms of macadamia nut toxicity, it is essential to consult your veterinarian. For asymptomatic dogs that have recently ingested more than 1 to 2 grams per kilogram of their body weight, inducing vomiting may be recommended, and activated charcoal can be beneficial for significant ingestions. Most symptomatic dogs tend to recover without specific treatment, but severely affected animals may require supportive care, including fluids, analgesics, or antipyretics. Fortunately, muscle weakness, while painful, is typically short-lived, and most patients fully recover from the toxicity.
Xylitol
Why/How is it toxic?
Xylitol is a sugar substitute commonly found in sugar-free gum, sweets, baked goods, and other low-calorie or diabetic-friendly products. While xylitol is safe for human consumption, it can be extremely toxic to dogs. The reason behind this toxicity is related to how xylitol is metabolised in dogs' bodies. When dogs ingest xylitol, it causes a rapid and excessive release of insulin from the pancreas. This insulin surge can lead to severe hypoglyceamia, a condition characterised by dangerously low blood sugar levels. Moreover, xylitol can also damage the dog's liver, potentially causing liver failure. These harmful effects of xylitol on dogs have been discussed in a study by Dunayer and Gwaltney-Brant in 2006.
How much is toxic?
The toxicity of xylitol in dogs is dose-dependent, meaning the amount ingested plays a crucial role in determining the severity of the poisoning. Even relatively small quantities can be harmful. As little as 0.1 grams of xylitol per kilogram of a dog's body weight can lead to a significant insulin release. The toxic dose can vary from one dog to another, but ingesting around 0.5 grams of xylitol per kilogram of body weight or more can be lethal. Therefore, it's essential to be cautious when products containing xylitol are present, especially if you have a smaller dog.
What symptoms will I see?
The symptoms of xylitol poisoning in dogs can manifest rapidly and may include vomiting, loss of coordination, depression, lethargy, seizures, and even collapse. Since the most immediate concern is the risk of hypoglycemia, signs such as disorientation, staggering, and loss of consciousness can be particularly alarming. Liver failure symptoms, such as jaundice (yellowing of the eyes and gums), can develop within a few days. The degree of toxicity and the onset of symptoms can vary based on the amount of xylitol ingested.
What should I do?
If you suspect that your dog has ingested a product containing xylitol, it is essential to seek immediate veterinary care. Time is of the essence in treating xylitol poisoning. Your veterinarian may induce vomiting if the ingestion was recent and administer intravenous fluids and intravenous dextrose to try and stabilise blood sugar levels. Supportive care and liver protectants might also be needed, depending on the severity of the poisoning. In any case, prompt professional intervention is the best course of action to ensure your dog's safety and recovery.
Food Mould
Why/How is it toxic?
Moulds are fungi that grow on a variety of foods, and while some moulds are harmless, others can produce mycotoxins, which are harmful substances. A common mycotoxin encountered in food moulds is aflatoxin. Aflatoxins are potent carcinogens that can also cause acute poisoning in dogs. These mycotoxins can be found in various food items like corn, peanuts, and tree nuts and can be transmitted through contaminated pet food.
How much is toxic?
The level of toxicity can vary widely depending on the type and amount of mycotoxins ingested. Dogs have varying sensitivities, so there is no exact threshold for aflatoxin toxicity. In general, ingestion of small amounts may lead to minor symptoms, while larger quantities can result in severe consequences.
What symptoms will I see?
Symptoms of mycotoxin poisoning may manifest in different ways and can include: tremors and ataxia (wobbliness), Vomiting, Diarrhoea, lethargy and seizures. Severe aflatoxin exposure can cause liver damage, which may ultimately be fatal. Acute aflatoxin toxicity can be life-threatening, while prolonged exposure to low levels of aflatoxins can lead to chronic liver issues. Acute ingestion of smaller quantities causing milder symptoms is entirely treatable.
What should I do?
If you suspect your dog has consumed mouldy food or is displaying symptoms of mould toxicity, it's essential to seek immediate veterinary attention. Your vet can perform blood tests to assess liver function and other diagnostic tests to evaluate the severity of the situation. Treatment may involve hospitalisation and supportive care, including intravenous fluids to maintain hydration and medications to address symptoms like vomiting and diarrhoea. The best approach is prevention. Be cautious about the food you provide to your dog, check for any signs of mould, and store pet food in a cool, dry place to reduce the risk of mould growth.
Corn on the cob and peach stones
Why/How is it dangerous?
Whilst it might seem like an unlikely pairing. The method of danger of these two food items is the same, hence grouping them together. Corn cobs and peach stones may seem harmless, but they can pose a severe threat to your dog's health. When dogs ingest these items, they often struggle to digest them properly and they can obstruct the gastrointestinal tract.
How much is dangerous?
The amount needed to cause harm can vary depending on your dog's size, age, and overall health. Even a small piece of corn cob or a single peach stone can be dangerous if it becomes lodged in your dog's intestines. Keep in mind that it's always better to err on the side of caution and prevent your dog from accessing these items altogether.
What symptoms will I see?
If a gastrointestinal blockage has occurred you will see the following symptoms: acute and persistent vomiting, abdominal pain, lethargy, refusing food.
What should I do?
If you suspect your dog has ingested a corn cob or peach stone or is displaying any of the mentioned symptoms, contact your veterinarian immediately. Depending on the severity of the situation, your vet may recommend inducing vomiting if the item was recently consumed or conduct diagnostic tests like X-rays to assess the extent of the blockage.
Prevention is your best ally. Keep these hazardous items out of your dog's reach, and be vigilant when disposing of food scraps and when at family barbeques! A little caution can go a long way in keeping your furry friend safe from these unexpected dangers.
What next?
If you are concerned about any of the foods mentioned above or have another query and are based in the UK then you can either call your local vets or you can call the Animal Poison Line for detailed and specific advice on an individual toxin. Their website can be found here. They charge between £35-£45 per call and will want you to have the following information:
Your pet’s details: Name, age, breed and weight.
What your pet has eaten or been exposed to? e.g. the drug or product/brand name.
How has your pet absorbed the potential toxin? e.g. Have they eaten, inhaled or has it been on their skin.
How long ago was your pet exposed to the potential toxin? e.g. estimated minutes, hours.
How much of the potential toxin have they been exposed to? e.g. unit of measure and estimated amount.
Is this the first time your pet has been exposed to this toxin? e.g. If this has happened in the past, when.
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