21 October 2021
The following is a list is meant to help pet parents recognize some of the foods that are dangerous to dogs and cats and most commonly implicated with poisoning and adverse effects in pets; however, it is not an exhaustive list. Please consult your pet nutritionist or veterinarian before feeding your pet any food not specifically intended for pet consumption.
IF YOU SUSPECT YOUR PET HAS INGESTED ANY OF THESE SUBSTANCES, CONTACT YOUR VETERINARIAN IMMEDIATELY.
Chocolate, which is made from cocoa, is a common cause of toxicity in dogs1. The main toxic agent in cocoa products is theobromine, a methylxanthine that stimulates the central nervous system and causes tachycardia (rapid heart beating), respiratory stress, and hyperactivity. As summarized in the Merck Veterinary Manual, observable signs of poisoning include vomiting, diarrhea, excessive thirst, and restlessness and usually develop within 6-12 hours of ingestion2. Darker chocolate and cocoa powder contain more concentrated amounts of theobromine and will lead to more severe reactions, such as abnormal heart rhythms, tremors, seizures, collapse, and in some cases, death3. Dogs, with their eager-to-eat natures, seem to be more likely to consume cocoa-containing products than cats and other pets2, but it is still known to be toxic to many animals so should not be fed to any pets.
Caffeine –is another methylxanthine alkaloid, like theobromine in cacao. The mechanism of toxicity and clinical signs are the same as theobromine3.
Onions, chives, leeks, and garlic are members of the Allium genus of plants, of which all forms (raw, cooked, dehydrated) are dangerous to dogs and cats4. Allium species contain various organosulfur compounds that cause oxidative damage within red blood cells, resulting in hemolytic anemia5,6. In cases where large amounts of any of these plants are ingested, signs may appear within one day of consumption; however, it is more common for clinical signs to develop after several days7. As summarized by Kovalkovičová et al., first observable signs include vomiting, diarrhea, abdominal pain, loss of appetite, depression, and dehydration, later followed by pale mucous membranes, difficulty or rapid breathing, sluggishness, dark-coloured urine, jaundice, weakness, rapid heart rate3. Even small amounts of these vegetables can pose a threat to your pet; ingestion of onions greater than 0.5% of an animal’s body weight is considered toxic8.
Studies of avocado toxicity are well documented in birds, as well as horses, rabbits, guinea pigs, and fish; however, there are only a handful of reports in dogs and no cases have been reported for cats2. The toxin persin is present in the fruit, pit, bark, and leaves9,10. Cases of vomiting and diarrhea have been observed in dogs following avocado ingestion; however, more research is needed to provide conclusive evidence of toxicity. One study of two dogs from separate homes reported suspected toxicity due to avocado ingestion, citing in fluid accumulation in the lungs and chest, leading to difficulty breathing and death due to oxygen deprivation. The two dogs affected also had a history of underlying health conditions11.
Acute renal (kidney) failure following ingestion of the fruits of Vitas vinifera (grapes, raisins, currants, and sultanas) has been reported in many dogs, with some cases even resulting in death12,13, but much about these cases remains a mystery. The mechanism of toxicity has not been identified, a dose-response relationship has not been established, and furthermore, not all dogs seem to be affected14. Nonetheless, because of the volume and serious nature of reported cases, all incidences of grape or raisin ingestion by dogs should be considered potentially life-threatening2. As summarized by the Merck Veterinary Manual, pets suffering from a negative reaction to grape or raisin ingestion will develop vomiting and/or diarrhea within 6 to 12 hours. They may also exhibit a lack of energy, loss of appetite, abdominal pain, weakness, excessive thirst, and tremors, with kidney failure occurring in severe cases and resulting in death2. Two reports of suspected Vitas poisoning in cats and one death of a ferret have also been reported15.
A sweetener commonly used to replace sugar in products such as chewing gum, breath mints, candies, baked goods, and peanut butter, xylitol can pose a serious threat to dogs. Unlike humans, in dogs, xylitol promotes insulin release resulting in a rapid decline in blood sugar levels16,17. In more serious cases, liver damage, blood clotting disorders, and even death have been reported18. As summarized by the Merck Veterinary Manual, signs of low blood sugar can begin in as little as 30 minutes and include sluggishness, loss of motor control, vomiting, and seizures2. The dose required to achieve toxicity in dogs is 0.05 g per lb of body weight19. The average piece of chewing gum or breath mint contains between 0.22 to 1.00 grams of xylitol. Therefore, a 10 lb dog would only have to eat one piece of gum to achieve a potentially toxic dose20. There are no studies in the current literature of cats presenting xylitol toxicity.
All alcohols have damaging effects on the central nervous system of dogs and cats21. One of the most common household alcohols is ethanol, which is present in many commonly found foods and substances including alcoholic beverages, rotting fruit, and even raw dough22. While some pets accidentally find their way into sources of alcohol, like the case of a dog eating rotting apples from the backyard23, cases of owners intentionally giving their pets alcohol have also been documented3. As described by the Merck Veterinary Manual, observable signs of alcohol poisoning include vomiting, diarrhea, difficulty breathing, excessive thirst, disorientation, and incoordination, and may result in liver failure, coma, and death21.
In addition to alcohol poisoning, beer specifically, presents an added threat – hops. Hops are flowers often used in the brewing process that impart compounds that are dangerous to dogs24, as well as presenting a threat if the hops themselves are consumed; so beware if you’re a home brewer22. As described by Cortinovis and Caloni, within hours of consumption, pets may exhibit signs such as hyperthermia (high temperature), anxiety, rapid heartbeat, rapid breathing or panting, vomiting, abdominal pain, dark urine, and seizures, and risk of death is high22.
Raw dough presents another dual-risk to animals as the warm, moist environment provided by the stomach provides good conditions for the yeast, Saccharomyces cerevisiae that causes dough to rise to do so in the stomach which leads to the production of ethanol and carbon dioxide3. In addition to the ethanol poisoning this may result in, carbon dioxide and the expansion of the dough can cause gas, bloating, blockage of the digestive tract, and potentially stomach rupture25.
Like grapes and raisins, many cases of poor reactions following ingestion of macadamia nuts have been reported in dogs; however, the mechanisms of toxicity have not been identified22. As described in the Merck Veterinary Manual, signs of toxicosis following macadamia nut ingestion often arise within 12 hours and include weakness, depression, vomiting, loss of motor control, tremors, and hyperthermia (high temperature). These usually resolve within 12-48 hours and no fatalities have been reported to date26.
With the recent legalization of marijuana in Canada and parts of the USA, the reports of marijuana toxicity in pets have greatly increased27. The majority of these cases feature dogs; however, there are also reports of adverse effects in cats28,29. While marijuana ingestion is rarely lethal, many cases involve the consumption of marijuana in combination with chocolate or xylitol in the form of a baked good, resulting in more severe signs30.As reported by Janczyk et al. signs of marijuana intoxication may include head bobbing, vocalization, loss of appetite, depression, drowsiness, disorientation, loss of motor control, rapid heartbeat, tremors, urinary incontinence, hypothermia (low temperature), seizures and, rarely, coma. Signs may persist for up to 96 hours following exposure31.