A few days ago, I heard about a dog that died after eating a cake that was sweetened by xylitol. I had not heard before that dogs cannot tolerate xylitol and therefore I searched the scientific literature to get an overview about food items that can be very toxic for dogs but not for humans.
As there are huge differences between size, breeds and even in between individuals, it is possible that one dog can eat quite a lot of a specific food item without showing any symptoms while another could die already from a much smaller amount. Therefore, one should not feed the following food items to dogs and also store them out of reach for the dogs. It is also important to remember that the amount plays a very important role when talking about toxic food items; small amounts of one food item can be well tolerated while the same amount of another can already lead to serious damages.
It is possible that the list below is not complete, but I will monitor the research about this topic and update the list if I find any new results. I would be happy if you send me an email to email@example.com if you hear about new studies about food items that are toxic for dogs.
You can read the original articles written in academic English here and here.
This plant family contains onions, garlic, leek and chive. They contain sulfur compounds that damage the red blood cells and are not destroyed by drying or cooking the food. 15-30 g onions per kg body weight are enough to cause damage, although some breeds are much more sensible (eg. Akita, Shiba, Jindo). Aussies are very fond of food, but I have yet to meet a dog that would voluntarily eat raw onion or leek. As already described in the beginning, it is very important to consider the amount that is eaten by your dog. I would not give onion soup or a dish made of only leek, but if a sauce contains a small amount of onion or garlic, it should not cause any problems.
Ethanol (in everyday language also alcohol) is of course present in alcoholic beverages, but can also be in paints, medication, perfume, mouthwash, thermometers, antifreeze and disinfectants. Alcohol is also formed when fruits rotten (for example apples) and in uncooked yeast dough. It is unknown exactly how alcohol is harming dogs, but believed that receptors in the brain are blocked.
Grapes, raisins, sultanas and currants (raw, but also cooked/baked) can lead to kidney failure in dogs. Also here it is unknown how the kidneys are damaged. There are big individual differences in the sensitivity to grapes and raisins. There have been cases reported where dogs ate up to 1 kg of raisins and showed no symptoms and others that died after eating only a handful. Earlier, I sometimes gave a grape or a raisin to my dogs because I did not know that already very small amounts can be toxic for some dogs. After reading these two articles, I will however not do this anymore. You never know if your own dog might be extremely sensitive. Unfortunately, I have not found any information about different breeds and if Aussies are especially sensitive to grapes.
Hops is needed for the brewing of beer and both fresh and spent hops seem to lead to malignant hyperthermia in dogs (excessive heat production). Some breeds are especially affected: Greyhound, Labrador Retriever, Saint Bernard, Pointer, Doberman, Border Collie, English Springer Spaniel und nordic breeds. Unfortunately, I have not found information how sensitive Aussies are.
Most commercially available macadamia nuts only contain a small amount of the toxic substances, but some cases have been reported from Australia, where macadamia trees grow. Until now, it is not sure how many macadamia nuts are needed and how the symptoms arise in dogs. Until now, no cases are known where dogs died after eating macadamia nuts.
Caffeine, theobromine and theophylline:
You can find these plant-derived substances in different food products, beverages and medications. Coffee, tea, guarana and many soft drinks (Coke, Red bull, …) contain caffeine. Theobromine is in cacao seeds and chocolate. Theophylline is in tea together with caffeine. These three substances all lead to an increased muscular contractility in dogs, a stimulation of the central nervous system and the cardiac muscle, relaxation of the smooth muscle and diuresis.
The darker the chocolate (especially baking chocolate and cacao powder), the more theobromine it contains and the more dangerous it is for dogs.
Even though many dog owners know that chocolate is toxic for dogs, most poisoning cases in households are still caused by chocolate (likely stolen) consumption! One really should store chocolate and other products that contain cacao somewhere where dogs cannot reach it.
It is now time for the food item that inspired me to write this blog article. Xylitol is an artificial sweetener, mostly present in chewing gum but also in candy, cookies, bread and similar. It is also known as Polysweet, Xylosweet, Xyla, birch sugar and E967. Xylitol has antibacterial properties and is well tolerated by humans. Therefore, many dental products contain xylitol. In the article, they even mentioned that some mouthwash for dogs contained xylitol. If you use these kind of products, make sure that it does NOT contain xylitol!
Xylitol is already toxic in very small amounts and as little as 0.03 g xylitol per kg body weight can lead to the increase of insulin so that the blood sugar level decreases dramatically. Additionally, liver failures can occur. When you have xylitol in your house, please be careful that your dogs cannot reach or eat it by accident.
Unfortunately there are a lot misunderstandings among dog owners about feeding bones to dogs. I will therefore also write a short paragraph on this topic. Dogs of course love to eat meat and it is a very nice, natural activity to chew on a bone. It is however very important that the bone is RAW. The structure of the bone is changed by the heat in cooking, frying or barbecuing. First, they are much more difficult to digest and second, they easily splinter into very sharp fragments. It is no problem to give raw chicken bones and many dogs really appreciate them. But after cooking, they can be very dangerous when they splinter. It is preferable to take bones with quite a lot of meat on them as they are easier to digest and taste better.
When dogs are not used to eat bones, it is best to give only a little bit (10-15 minutes chewing) until the dog is used to it and can digest the bone. Otherwise it may lead to diarrhea or throwing up. I never give bones without supervision, to be able to react quickly in case the dog would swallow the bone and it gets stuck in the airways. However, the risk for this to happen is, in my experience, extremely low as long as you adopt the size of the bone to the size of your dog.