Human Foods that Poison Pets

Feeding pets food that we enjoy is not only wrong, it can also be fatal. There are some foodstuffs that humans relish which cause illness and death if eaten by pets.

Chocolate, macadamia nuts, onions and grapes or raisins are good examples. Each of these foods contains chemicals which rarely cause problems for humans, but for dogs, these same chemicals can be deadly.

Of course we know that fat is no good for us humans but feeding our pets the fat from a ham, chop or steak can cause deadly pancreatitis.

Chocolate Toxicity

Chocolate contains theobromine, a compound that is a cardiac stimulant and a diuretic.

darkchocWhen affected by an overdose of chocolate, a dog can become excited and hyperactive. Due to the diuretic effect, it may pass large volumes of urine and it will be unusually thirsty. Vomiting and diarrhoea are also common. The effect of theobromine on the heart is the most dangerous effect. Theobromine will either increase the dog’s heart rate or may cause the heart to beat irregularly. Death is quite possible, especially with exercise.

After their pet has eaten a large quantity of chocolate, many pet owners assume their pet is unaffected. However, the signs of sickness may not be seen for several hours, with death following within twenty-four hours.

Cocoa powder and cooking chocolate are the most toxic forms. A 10-kilogram dog can be seriously affected if it eats a quarter of a 250gm packet of cocoa powder or half of a 250gm block of cooking chocolate. These forms of chocolate contain ten times more theobromine than milk chocolate. Thus, a chocolate mud cake could be a real health risk for a small dog. Even licking a substantial part of the chocolate icing from a cake can make a dog unwell.

Semi-sweet chocolate and dark chocolate are the next most dangerous forms, with milk chocolate being the least dangerous. A dog needs to eat more than a 250gm block of milk chocolate to be affected. Obviously, the smaller the dog, the less it needs to eat.

Onion and Garlic Poisoning

Onions and garlic are other dangerous food ingredients that cause sickness in dogs, cats and also livestock. Onions and garlic contain the toxic ingredient thiosulphate. Onions are more of a danger.

Pets affected by onion toxicity will develop haemolytic anaemia, where the pet’s red blood cells burst while circulating in its body.onionsandgarlic

When pets are first affected by onion poisoning, they show gastroenteritis, including vomiting and diarrhoea. The pets will show no interest in food and will be dull and weak. The red pigment from the burst blood cells appears in an affected animal’s urine and the animal becomes breathless. The breathlessness occurs because the red blood cells that carry oxygen through the body are reduced in number.

The poisoning occurs a few days after the pet has eaten the onion. All forms of onion can be a problem including dehydrated onions, raw onions, cooked onions and table scraps containing cooked onions and/or garlic. Left-over pizza, Chinese dishes and commercial baby food containing onion, sometimes fed as a supplement to young pets, can cause illness.


All forms of onion can be a problem including dehydrated onions, raw onions, cooked onions and table scraps containing cooked onions and/or garlic.


Onion poisoning can occur with a single ingestion of large quantities or with repeated meals containing small amounts of onion. A single meal of 600 to 800 grams of raw onion can be dangerous, whereas, a ten-kilogram dog fed 150 grams of onion for several days is also likely to develop anaemia. The condition improves once the dog is prevented from eating any further onion

While garlic also contains the toxic ingredient thiosulphate, it seems that garlic is less toxic and large amounts would need to be eaten to cause illness. In practical terms, garlic fed in the small amounts that owners often give their pets or at quantitiies present in some pet foods is not a danger.

The Danger of Macadamia Nuts

Macadamia nuts are another concern. A recent paper written by Dr. Ross McKenzie, a Veterinary Pathologist with the Department of Primary Industries, points to the danger of raw and roasted macadamia nuts for pets.

bigstock_macadamia_nuts_3671798The toxic compound is unknown but the effect of macadamia nuts is to cause difficulties with movement. Dogs develop a tremor of the skeletal muscles, and weakness or paralysis of the hindquarters. Affected dogs are often unable to rise and are distressed, usually panting. Some affected dogs have swollen limbs and show pain when the limbs are manipulated. In some respects, the condition resembles that seen with tick paralysis.

Dogs have been affected by eating as few as six macadamia kernels (nuts without the shell) while others have eaten approximately forty kernels. Some dogs had also been given macadamia butter.

Luckily, the muscle weakness, while painful, seems to be of short duration and all dogs recovered from the toxicity. All dogs were taken to their veterinary surgeon.

Pet owners should not assume that human food is always safe for pets. When it comes to chocolate, onions, garlic and macadamia nuts, such foods should be given in only small quantities, or not at all. Be sure that your pets can’t get into your stash of chocolates, that food scraps are disposed of carefully to prevent onion and garlic toxicity and that your dog is prevented from picking up macadamia nuts if you have a tree in your garden.

For those with an interest in toxic plants and their effects on animals, the book Poisonous Plants: A Field Guide by RM Dowling and RA McKenzie is available from the Department of Primary Industries in Queensland, Australia.

Grape and Raisin Toxicty

Grapes and raisin toxicity for petsThe toxicity of grapes and raisins is now well-recognised after suspicions were raised from 1989 onwards. The ASPCA Animal Poison Control Center took over 200 calls relating to grape and raisin toxicity between January 2001 and August 2004.

The cause of the toxicity is still not fully understood but the effects are well known.

Within a few hours of eating grapes or raisins, affected dogs will usually vomit and will be lethargic. They may develop diarrhoea and will usually show increased water consumption. Partially digested grapes or raisins are sometimes seen in the dog’s vomit. 

The risk with grape and raisin toxicity is renal failure and this can be fatal.

Grapes and raisins should be regarded as being toxic and should not be fed to dogs, cats and other pets.

A Fat Lot of Good

We know that fat is no good for us humans.Ham rinds cause pancreatitis in pets

So often we don’t think about the danger of fat for our pets.  The fat from a ham, chop or steak can cause pets to suffer from the deadly condition pancreatitis. It’s a very common malady and one to be avoided.

Pets are not immune to the dangers of fat. Fat is dangerous and deadly.

If you are trimming the rind off a ham for Christmas or removing the fatty tail of a steak or chop – don’t give that to your dog or cat.

Also be certain that your rubbish bin containing fatty scraps is secured. Dogs and cats regularly raid garbage bins in their owner’s absence and the result of engorging on garbage and the decaying or fatty foods contained therein can be deadly – especially if you are not home to render assistance.

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Dr Cam Day

Dr Cam Day

Vet Behavioralist

Dr Cam Day is a Veterinarian consulting full-time in pet behaviour in South-East Queensland, Australia.