By Dr. Becker
Two researchers at the University of Milan in Italy compiled a list of human foods that cause the most pet poisonings worldwide, and released their findings in the journal Frontiers in Veterinary Science.1
"Several foods that are perfectly suitable for human consumption can be toxic to dogs and cats," wrote researchers Cristina Cortinovis and Francesca Caloni. "The poisoning episodes are generally due to lack of public knowledge of the serious health threat to dogs and cats that can be posed by these products."
Some cases of poisoning occur when an owner unknowingly offers a harmful food to a dog or cat, but in many cases, pets find accessible toxins around the house and help themselves.
The researchers found that in the past decade, reported cases of toxicity in pets across the globe have most often involved the following food items. Scientists don't know exactly why some of these foods, which are perfectly safe for most humans, can be deadly for dogs and/or cats:
✓ Chocolate and chocolate-based products
✓ Plants containing allium, including onions, garlic, leeks and chives
✓ Macadamia nuts
✓ Vitis vinifera fruits, including grapes, raisins, sultanas and currants
✓ Foods and product containing the sweetener xylitol
✓ Ethanol in alcoholic beverages
Chocolate is made from the roasted seeds of the Theobroma cacao or cocoa tree. The seeds have certain properties that can be toxic for dogs and cats, including caffeine and theobromine, which are naturally occurring stimulants.
Both theobromine and caffeine stimulate the central nervous system and heart muscle. They also relax smooth muscles, especially the bronchial muscles, and increase production of urine by the kidneys.
Dogs are more often the victims of chocolate poisoning than cats, because dogs like sweet-tasting things, and they are indiscriminate eaters to begin with. Studies have shown that dogs are especially sensitive to theobromine compared to other domestic animals.
This is because dogs metabolize the substance very slowly, which means it stays in their bloodstream for an unusually long time. This may also be true of cats, but because kitties don't commonly overdose on chocolate, there isn't a lot of research on feline chocolate toxicosis.
Plants Containing Allium
This is a tricky one. Plants of the genus allium, which includes onions, chives, garlic and leeks, make some pets sick (there have even been fatalities), while others don't seem affected. Symptoms of allium poisoning can occur a day or several days after ingestion, depending on the amount eaten.
Initial symptoms usually include vomiting, diarrhea, abdominal pain and loss of appetite. These signs can be followed by weakness, rapid breathing, high heart rate, pale mucous membranes, reddish or brown urine and anemia.
The toxic compounds in allium plants are organosulfoxides. When chewed, organosulfoxides convert to a mixture of sulfur compounds that can damage your dog's or cat's red blood cells. According to LiveScience:
"If [a] dog or cat ingests even just a piece of an onion (specifically, 5 grams of onion per kilogram of body weight for cats, or 15 to 30 grams per kg for dogs), it can cause dangerous changes to their blood."2
The University of Milan researchers found that between 1994 and 2008, there were 69 reported cases of dog poisonings and four cat poisonings from foods containing allium.
The poisonings were a result of a variety of foods and preparation methods, including raw and baked garlic, Catalan spring onions (calcots), onion soufflé, butter-cooked onions and steamed dumplings seasoned with Chinese chives. The organosulfoxides in allium plants seem to survive both cooking and drying.
Garlic can cause changes in blood parameters when fed in very large quantities (much more than pets would naturally eat) or if it is given in a garlic supplement (which I never recommend).
One study demonstrated negative changes in blood parameters when dogs were given 5 grams of garlic per kg of body weight.3 This amount translates to eight cloves for a 12-pound dog! No dog I know would voluntarily consume this much and no owner I've ever met would voluntarily give this amount!
Dogs can healthfully consume 1/4 teaspoon of freshly chopped garlic per 15 pounds of body weight and reap substantial health benefits, just don't go overboard.
Macadamia nuts can cause serious problems for dogs, even in very small amounts. According to the study, more than 80 cases of poisoning were reported over a five-year period in Queensland, Australia, a major area of macadamia nut cultivation. Fortunately, no pet deaths have been reported.
Symptoms of poisoning occur with 12 hours of ingestion and can include hind-limb weakness, vomiting, stiffness and loss of coordination, trembling, fever, abdominal pain and pale mucous membranes.
Grapes and Raisins
The study authors write:
"While some foodstuffs, such as chocolate, have long been known to cause poisoning in dogs and cats, others, such as grapes, had previously been considered unlikely to cause problems, and have emerged as a potential concern only in the last few years."
I recently interviewed Melissa Gardner, an intelligence specialist with the FBI and a former military intelligence officer, who has a very interesting and plausible theory to explain why grapes and raisins, once safe to feed pets, are now toxic. She believes that fluoride-based pesticides used on grapevines could be to blame.
According to the University of Milan researchers, grapes, raisins, sultanas and currants — both raw and cooked — can cause kidney failure in dogs. However, not all dogs have the same reaction to these foods. For example, one study examined 180 cases of dogs who ate grapes and related fruits and reported that some dogs showed no symptoms after eating 2 pounds of raisins, while others died after eating just a handful.
This information seems to support Gardner's theory that it's the way the fruits are cultivated, rather than the fruits themselves, that render them toxic. Unfortunately, based on what Gardner uncovered during her investigation, we can't assume organic raisins or grapes are safe, either, so my recommendation is to avoid feeding grapes, raisins and related fruits to your pet.
Xylitol is a sweetener that is highly toxic to dogs. It's a sugar alcohol extracted from corn and corn fiber, birch, raspberries and plums.
Xylitol is used to sweeten a wide range of products, including sugar-free gum and mints, nicotine gum, chewable vitamins, certain prescription drugs, dental hygiene products and baked goods. It can also be purchased in granulated form as a sugar replacement to sweeten beverages, cereals and other foods.
Sadly, xylitol poisoning in dogs is reaching epidemic proportions. Just a few years ago, xylitol could be found in less than a hundred products in the U.S., primarily limited to sugar-free gums, candy and foods. Today it can be found in a wide range of health and beauty products, food products, over-the-counter drugs and supplements and prescription medications.
Until fairly recently, xylitol was found primarily in products not normally given to dogs. Poisonings were usually the result of dogs sampling human foods, candy or gum on the sly. However, this sweetener is now in certain peanut and nut butters. Symptoms of xylitol toxicity can develop from 30 minutes up to 12 hours after ingestion, and include vomiting and signs of hypoglycemia (low blood sugar), such as lethargy, inability to control movements, collapsing and seizures.
Alcohol (ethanol) poisoning in pets typically occurs when a dog (or much less likely, a cat) samples an alcoholic beverage. Toxicity has also occurred in dogs who ate rotten apples, sloe berries and uncooked bread and pizza dough, all of which contain alcohol. Other potential sources of ethanol include paint and varnish, certain medications, perfume/cologne, mouthwash and certain types of antifreeze.
Just as with humans, when a pet ingests alcohol, it is quickly absorbed from the GI tract and reaches the brain. Symptoms develop within a short period of time, and include depression, loss of coordination, lethargy, sedation, increased body temperature, dangerously slow breathing and coma.
If You Think Your Pet Has Been Poisoned
If you suspect your dog or cat has ingested a poison and you have questions or need guidance, you can call the American Society of the Prevention of Cruelty to Animals' (ASPCA) Poison Control Center hotline at 1-888-426-4435, or the Pet Poison Helpline at 1-855-764-7661. Both hotlines can be reached 24 hours a day, seven days a week, 365 days a year.
If you're sure your pet has been exposed to a toxin, get her to your veterinarian or an animal emergency hospital immediately. If you know or suspect the substance your animal got into, bring it along.