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Foods that Spell DANGER to dogs and cats

Whilst some foods are great for us humans, they may be harmful or even toxic to our dogs and cats…

Onions and Garlic

It is well known that Onions can be fatal to dogs and cats.  This is because onions destroy red blood cells and can cause anemia, weakness, and breathing difficulties.   Some veterinary experts warn that even small amounts can cause cumulative damage over time. The problem appears to include several members of the onion family, including onions and chives – raw, powdered, dehydrated, or cooked – the problem being worse with onion that is cooked, dehydrated and (most particularly) when powdered..  The question then becomes, does the same situation apply in the case of garlic, which is a member of the onion family – speaking botanically.
And the answer is Garlic can be harmful to dogs in large amounts.

A small amount of Garlic has been used safely for many years in home produced dog foods, where it has been included because of its well known health enhancing properties.   In all these cases there has been nothing seen that would lead to the suspicion that the garlic component of those foods has in any way been toxic.  However, having said that, an excessive amount of garlic like any other food (salt would be an excellent example) if included at excessive levels can cause problems.    In the case of garlic, it has been safely included at low levels in canine diets for many years because garlic contains only a small amount of the problematic substance that is in onions (each food component has its own unique problem when supplied in excess).  The safe level is no more than one percent of a mixture composed of ground meat and bone and vegetable materials etc.

The bottom line is that with garlic (as with so many other dietary components), moderation, or more precisely, the correct dietary level (dietary balance), of garlic, is the key to enhancing health and ensuring an absence of toxic side effects.

Grapes – including any dried from of grapes

For many people, especially those who have thrown the occasional grape to a dog whilst eating grapes themselves, finds even today, the thought of grapes being a problem for canines simply ludicrous. What could be a healthier, more wholesome reward for a well-behaved dog? Sadly, that turns out not to be the case.  In 12 months, the ASPCA’s Animal Poison Control Center (USA) documented 140 cases of grape/raisin toxicity. More than one-third exhibited serious symptoms, including kidney failure, and seven died.

While it is still unclear what makes grapes and their weathered friends sultanas and raisins so toxic to dogs is unknown. However, it is clear that these fruits contain a fungus, pesticide, or some other toxin that negatively affects a dog’s kidneys. And it doesn’t take much; just one ounce for every 2.2 pounds of body weight can induce toxic symptoms, including vomiting, belly pain, and diarrhea. In severe cases, dogs have experienced severe renal failure and death.

Recent research suggests that only some dogs and not all will be affected by grapes.  In essence, the problem is genetic.  It will be those dogs that lack the enzymatic machinery to detoxify the poisonous principal – whatever it is – that are likely to (will) suffer from grape poisoning.
However, until we can be certain of this and have a way of detecting (safely) those dogs likely to be harmed by grapes, the strongest advice we can hand out is do not feed any member of the grape family (in any form) to any dog.


Chocolate can cause seizures, coma and death. Cooking or dark chocolate is the most dangerous. The darker the chocolate, the more dangerous it is. But any chocolate, in large enough amounts, can kill a dog. There have been reports of an ounce of cooking chocolate poisoning a 30-pound dog, and most dogs will happily consume more than this. The symptoms may not show up for several hours (and so might make you think all is well), with death following within twenty-four hours.  If there is any suspicion that a dog has consumed chocolate, Veterinary attention should be sought as soon as possible.

Spinach and Oxalic Acid

Many people are concerned about the level of oxalic acid in spinach, particularly the possibility that this may be problematic if spinach is included as part of a raw food or BARF Program of Nutrition.

So the question is: “Should cat and dog owners be concerned about spinach or steer clear of spinach because of its oxalic acid content?”

The short answer is – No.

The longer answer is as follows…
In Australia, what is normally referred to as Spinach is actually Silverbeet, although English Spinach is becoming a more popular offering in the major supermarkets – mostly as an extended-life product via gas flushed cellophane bags.

Foods that are rich in Oxalic acid include tea, cocoa, rhubarb, spinach and silverbeet.  It occurs in substantial amounts in celery leaves, beetroot tops and parsley.
It should also be noted that Excessive quantities of Vitamin C are metabolized to oxalic acid; however, “mega doses of vitamin C (several grams per day) are probably a greater hazard than foods that actually contain oxalic acid.  On the other hand, rhubarb leaves, are most definitely toxic/ poisonous because of their high concentration of oxalic acid.  Fortunately, high levels of oxalic acid makes food very bitter, which is a deterrent to its consumption by most animals and people.
The problem with oxalic acid is that it forms insoluble complexes with various minerals in food such as calcium and iron.  This has the potential to cause calcium and iron deficiencies because when these minerals are attached to oxalic acid, they become unavailable to the body.   However, it should be pointed out that this is far more of a problem with cooked food than raw food.  However, whether one is a human or an animal, many kilos of cooked spinach or silver beet would have to be consumed, for these vegetables to have any sort of adverse effect on the body.
Another point to note is that a small number of dogs, cats and humans have a genetic tendency to form oxalate stones or uroliths in the urinary system.  It is often this fact which gives rise to the concern re oxalic acid rich foods in BARF formulations.


Avocados have been found toxic to dogs (fruit, pit, and plant) and it appears that the toxic component is a substance, which has been called ‘Persin’.  Studies to date indicate that Persin can damage heart, lung and other tissue in many animals.
Reported symptoms of Persin toxicity have included difficulty breathing, abdominal enlargement, abnormal fluid accumulations in the chest, in the abdomen and in the sac around the heart – the pericardium.
It is not know how much needs to be ingested in order for these toxic effects to be seen.  Nor is it known exactly how it produces its adverse effects. Mostly GI signs are  seen and the et will treat them systematically. In addition, the animal should be monitored closely for other clinical signs related to the cardiovascular system. (This information comes from veterinarians, the American Veterinary Medicine Association, and the ASPCA Animal Poison Control Center.)

Other reported problems with Avocados have related to their fat content.  In these cases the problems seen were stomach upset, vomiting and pancreatitis.
Note: According to the ASPCA, “Some dogs can eat [avocados] without having any adverse reactions. …. The Guatemalan variety, a common one found in stores, appears to be the most problematic. Other strains of avocado can have different degrees of toxic potential.”

Green Tomatoes and Green Potatoes

Both of these are both poisonous.  The green potato contains a toxin called solanine.  While most people are aware of the dangers posed by green potatoes, the fact that tomatoes can also be poisonous is not so well known.

Green tomatoes (and the tomato plant itself) can be poisonous to dogs. Tomatoes are members of the deadly nightshade family – and like potatoes, when they are green they contain a poisonous alkaloid – which, in the case of the tomato is called tomatine.   Tomatine is, an alkaloid related to solanine – the green poisonous principal in potatoes.
As the tomato fruit ripens, the tomatine disappears, in other words, ripe tomatoes are much safer than green tomatoes.
The clinical signs of Tomatine poisoning include lethargy, drooling, difficulty breathing, colic, vomiting, diarrhea (or constipation), widely-dilated pupils, paralysis, cardiac effects, central nervous system signs (e.g., ataxia, muscle weakness, tremors, seizures, coma and death. (This information comes from veterinarians, and the ASPCA Animal Poison Control Center.) (All parts of the plant except the tomato itself are poisonous to humans, although some people are sensitive to the ripe fruit also.)
Tomatoes also contain atropine,which can cause dilated pupils, tremors, and heart arrhythmias. The highest concentration of atropine is found in the leaves and stems of tomato plants, with less in unripe (green) tomatoes, and even less in ripe (red) tomatoes.


Can cause tremors, seizures and death.


Can be harmful to dogs. It stimulates the central nervous and cardiac systems, and can cause vomiting, restlessness, heart palpitations, and even death within hours.


The sweetener, can harm dogs. It is usually found in Diet products.  It can cause a sudden drop in blood sugar, resulting in depression, loss of coordination and seizures. Unless treatment is given quickly, the dog could die.

Macadamia nuts

Can harm dogs Macadamia nuts can cause weakness, muscle tremor and paralysis. These symptoms are usually temporary.


Walnuts can be poisonous to dogs .When dogs eat the seed hulls, they can get an upset stomach and diarrhea. The real problem is the fungus or mold that attacks walnuts after they get wet (from rain or sprinklers), which produces toxins. If the fungus or mold is ingested by a dog, it can become very ill and possibly die. Signs that should alert you to walnut poisoning are vomiting, trembling, drooling, lack of coordination, lethargy, loss of appetite, and jaundice (this is where the dog has yellowing eyes and gums). Severely affected dogs can produce blood-tinged vomit or stools. Dogs can take several days to exhibit serious signs of illness.

Fruit pits can be toxic to dogs –

These include apple seeds, cherry pits, peach pits, pear pips, plums pits, and apricot pits.  These all contain a compound capable of releasing cyanide in the body (cyanide is highly toxic). While a few apple seeds may not cause a problem, the effects can accumulate over time if they are given to dogs regularly. Dogs should not be allowed to chew on a peach pit, cherry pit, apricot pit, or plum pit. Chewing can allow ingestion of cyanide. Chewing could also result in the pit being swallowed, causing continuous exposure to cyanide, or could cause the dog to choke.

Too much Salt is harmful to dogs

Too much salt can cause kidney problems. Also, large breeds of dogs that eat salty food may then drink too much water and develop bloat, which is fatal unless emergency treatment is given very quickly.

Too much Fat can is harmful to dogs. Too much fat or fried foods can cause pancreatitis.

Ham and Bacon are not ideal for dogs.

Ham and bacon contain too much fat and too much salt, and can cause pancreatitis. Also, large breeds of dogs that eat salty food may drink too much water and develop bloat – which can be life-threatening.

Wild mushrooms can be fatal to dogs.

Wild mushrooms can cause abdominal pain, drooling, liver damage, kidney damage, vomiting, diarrhea, convulsions, coma, or death.

Large amounts of Grains are bad for dogs.

Grains should not be given in large amounts or make up a large part of a dog’s diet, but rice is generally safe in small amounts.

Cooked bones can kill dogs.

Cooked bones can splinter and tear through a dog’s internal organs or set like concrete in the large bowel.

The above is by Dr Ian Billinghurst

It really is simple enough to avoid these foods in your dogs diet, so don’t be over concerned. Some readers may also say that they have fed some of the above foods to their dogs without any problems, that may be so but this could also be part luck. I believe if it isn’t good for my dog, I don’t put it in their food.

Steve Courtney


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