Phone: (02) 4832 1977 

Dangerous foods - chocolate, onions, grapes and raisins

Some human foods are just not meant for pets. Chocolate, onions, grapes and similar dried fruit are only a few of the foods that can be fatal in cats and dogs. Felines are fussier eaters so toxicity is more often seen in dogs, but don’t be complacent – some of these foods have the same harmful effects in cats.


Chocolate can be lethal. Like coffee and tea, chocolate contains alkaloids such as theobromine and caffeine that are cardiac and nervous stimulants as well as diuretics. They cause dogs and cats to become excited and hyperactive, with severe cases progressing to seizures. The diuretic effect leads to the passing of large amounts of urine and intense thirst. Vomiting and diarrhoea are other common symptoms, while the effect on the heart can cause dangerously fast, weak and irregular heartbeats.

Symptoms take several hours to manifest, and large doses can lead to death within 24 hours.

How much chocolate is dangerous to dogs? A 10kg dog – a small to medium terrier – only needs around 250gm of cocoa or 125gm of cooking chocolate to become seriously ill. Cocoa, cooking and dark chocolate are the most dangerous, but a 250gm bar of milk chocolate can also cause illness. The chocolate can also be in the form of chocolate biscuits such as Tim Tams, or other foods containing chocolate.

If you see your pet eat chocolate, ring us immediately – there is no antidote to chocolate toxicity, so early intensive treatment is essential for survival. The prognosis improves if the chocolate is removed by inducing vomiting within 1 to 2 hours – and we can do this safely and quickly.

Onions and garlic

Onions – whether dehydrated, raw, cooked or fed as part of table scraps – are highly dangerous to dogs and cats. While considered not as toxic as onion, excessive amounts of garlic can also cause illness.

Both foods contain thiosulphate, a substance that causes red blood cells to rupture, leading to haemolytic anaemia. Lethargy, vomiting and diarrhoea are the first symptoms, progressing after a few days to weakness, disinterest in food, and urine that is reddish brown from the burst blood cells.

One onion feast of 600gms is enough to cause illness, or repeated small feeds of 150gms can lead to serious anaemia.

As there is no antidote, treatment for onion toxicity is supportive and includes I/V fluids and/or blood transfusion if the anaemia is severe. If onion or garlic is removed from the diet early enough, the pet’s condition will improve.

Grapes, raisins, currants and sultanas

All the above fruits – grapes, raisins, currants and sultanas – are members of the Vitis vinifera family and all have the potential to cause acute renal failure in dogs.

There is as yet little understanding of why these fruits are so dangerous to dogs, but the numerous records both within Australia and internationally documenting cases of poisoning mean we can’t underestimate their importance as toxic foods.

The onset of symptoms following ingestion of any of the grape family fruits can often be delayed for 24 to 72 hours. This can sometimes make it difficult to connect the illness with the eating of the fruits. The fruits can be toxic eaten straight (some dogs have been known to graze the vines in their owner’s vineyard), or as ingredients in cakes. Further complicating diagnosis is the apparent differences in the amount required to cause toxicity between individual dogs – from a few grapes to much larger amounts.

Despite variability in tolerance, it does appear that the more concentrated, dried fruits are more harmful than fresh grapes.

Clinical signs

Initial symptoms include vomiting, diarrhoea, abdominal pain and excessive drinking. Specific signs of renal failure develop after 24 hours and include weakness, depression, refusal to eat and low (or nil) urination. At this stage, blood biochemistry shows specific changes relating to kidney failure.


If presented soon after the fruits are eaten, the animal can be made to vomit. Intensive intravenous fluid therapy is instituted and maintained for at least 48 hours to support renal function, and other intensive care provided as required.

As with all toxins, the earlier treatment commences, the better the chance of survival and a full recovery.

If you suspect your pet has consumed any amount of grapes or raisins, please contact us immediately.