Common Household Food Items that are Toxic to Dogs and Cats
There are several foods that are suitable for humans, but which may pose a threat to the health of dogs and cats as they are toxic. The most common are chocolate and cocoa based products, xylitol sweetened products, onions and garlic, grapes and raisins, macadamia nuts and ethanol. Episodes of poisonings occur either due to owners being unaware of the effects of these foods and feeding them to their pets, or if pets have accidental access to these foods. Cases are more commonly seen in dogs than cats, as they tend to readily eat potentially harmful foods. Some common items like chocolate have long been known to be toxic to dogs and cats, but in the last few years, certain foods that were once considered unlikely to cause problems, such as grapes, have emerged to now cause issues and have been wrongfully diagnosed for many years.
Onion (Allium cepa), garlic (Allium sativum) leek (Allium porrum) and chives (Allium schoenoprasum) are of the Allium family. These are strongly aromatic and contain organosulfoxides which make them toxic. The mechanism of action is that allium-derived sulphur compounds cause oxidative hemolysis with the development of methemoglobinaemia and Heinz body formation in the erythrocytes. Cooking and processing does not remove the toxic effect. Consumption of 5g/kg of onions by cats and 15-30g/kg by dogs can cause important hematologic changes. Symptoms and signs appear one to several days after consumption depending on amount ingested. Vomiting, diarrhea, abdominal pain, loss of appetite and depression are common signs, whilst pale mucous membranes, rapid breathing and heart rate, jaundice and dark urine are common in cases of anemia. No specific antidote is available for Allium toxicosis. Activated charcoal can be administered after vomiting has stopped. Once clinical signs manifest, treatment should be supportive and severely anemic animals may need a transfusion.
Grapes, Raisins, Sultanas and Currants
Grapes and their dried products can cause renal failure in dogs whether they are consumed raw or cooked. Published case reports have identified renal failure with ingestion of estimated doses of raisins as low as 2.8mg/kg and as little as 4-5 grapes in a dog weighing 8.2kg. Ingestion of any quantity of these fruits is harmful and treatment should be handled aggressively due to the wide variance in tolerance levels of these foods. Vomiting is a common sign, usually within 24 hours of ingestion, with diarrhea, anorexia, lethargy and abdominal pain being the clinical signs. This is followed by signs of renal insufficiency or failure within a short period. The use of emetics and repeated doses of activated charcoal is highly recommended, as well as intravenous fluid therapy for 48-72 hours.
Macadamia nut toxicosis has only been reported in dogs to date, with ingestion of as little as 0.7g/kg of nuts to produce clinical signs. These develop within 12 hours of ingestion and include weakness, depression, vomiting, ataxia, tremors, hyperthermia, abdominal pain, lameness and pale mucous membranes. Animals recover fully within 24-48 hour of veterinary intervention.
This is found in alcoholic beverages, pain medication, perfume, mouthwash, certain types of antifreeze, disinfectants and in the treatment of ethylene glycol poisoning. The most common cases result from accidental ingestion of alcoholic beverages, but also pets eating rotten apples or ingesting uncooked bread and pizza dough. Ethanol is rapidly absorbed from the gastrointestinal tract and crosses the blood-brain barrier. Signs develop within an hour of ingestion and include central nervous depression, lethargy, ataxia, sedation and metabolic acidosis. In animals having consumed uncooked bread dough, abdominal distension due to gas production is common. Haemodialysis is beneficial for rapid removal of ethanol in severe toxicosis cases. Administration of Yohimbine has been recommended as an arousal agent. Fortunately most patients recover when they are monitored and given supportive care.
Hops is used in beer brewing, and as home brewing becomes more popular, cases of accidental exposure can occur. Ingestion causes malignant hyperthermia in dogs, especially breeds such as Greyhounds, Labrador Retrievers, St Bernards, Dobermans, Border Collies and English Springer Spaniels, who are predisposed to the condition. Hops contains various compounds which may uncouple oxidative phosphorylation resulting in malignant hyperthermia. Signs include hyperthermia, anxiety, tachycardia, tachypnea, panting, vomiting, abdominal pain and seizures. Cases should be treated aggressively to decontaminate the intestinal tract. Ice baths and cold IV fluids should be given to help lower body temperature, and if possible, administration of dantrolene sodium which is a skeletal muscle relaxant.
Methylxanthines (Caffeine, Theobromine and Theophylline)
These plant derived alkaloids are found in various foods, beverages and human medications. Caffeine is found in coffee, tea and as an additive in many soft drinks. Theobromine occurs in cacao seeds and products such as chocolate. Theophylline is also found in tea along with caffeine and is also widely used as a bronchodilator in asthmatic medications. Most poisonings result from chocolate ingestion, with dogs being more commonly affected than cats due to their indiscriminate eating habits. These ingestions tend to occur around holiday times when there are more of these chocolate products around the home. Unsweetened baking chocolate and cocoa powder contain higher concentrations with about 14mg theobromine per gram. Mild clinical signs followed ingestion of 20mg/kg of theobromine and caffeine, while severe clinical signs were observed at 40-50mg/kg and seizures occurring at 60mg/kg. Initial clinical signs appear within 2-4 hours after ingestion and include restlessness, polydipsia, urinary incontinence, vomiting and sometimes diarrhea. As intoxication progresses, hypertension, cardiac arrhythmias, PVCs, ataxia, seizures and coma can be seen. Gastric lavage, multiple doses of activated charcoal and strict supportive care are the treatment protocols with prognosis being good if decontamination is obtained within 2-4 hours of ingestion.
This sugar alcohol is used as an artificial sweetener in sugar free gum, candy, baked goods, bread, as well as medical and dental care products. Dogs are particularly at risk of developing severe life threatening signs. In dogs, xylitol is a potent insulin release stimulator resulting in dramatic decreases in blood glucose levels, with doses as low as 0.03g/kg resulting in hypoglycaemia. Xylitol ingestion has also been associated with liver failure in dogs, with the lowest dose associated with this type of liver failure being 0.5g/kg. Signs of hypoglycaemia include lethargy, ataxia, collapse and seizures developing with 30 to 60 minutes after ingestion, and can be delayed by up to 12 hours after ingestion. Supportive care and monitoring are the main treatment options. Activated charcoal is not recommended due to its poor ability to bind to xylitol. In cases of hypoglycaemia, blood glucose levels and liver function should be monitored and intravenous dextrose where necessary.
Preventing exposure is key to reducing incidents of such poisoning, but first and foremost it is imperative to educate pet owners about what foodstuffs to not feed to their pets. In the case that a pet ingests any of these foodstuffs, obtaining an accurate history is important, recognising the clinical signs early and getting appropriate veterinary treatment as quickly as possible can ensure a good prognosis.
Link to full original research article:
Front. Vet. Sci., 22 March 2016