Grape Sultana & Raisin Poisoning

Updated December 31, 2020

‘Essential facts (Details Below)’ 

When A Dog Eats Grape Products

1. Grapes are toxic whether dried, fresh or cooked
2. The toxic dose is unknown and highly variable
3. Removal via vomiting and treatment of kidney damage gives good results

Now dive deeper…

Why Grapes Are Toxic

Why grapes are toxic to dogs remains a mystery. Not just grapes, but also raisins, sultanas and currants, even when baked into cakes or biscuits. Here in South Australia, an added hazard is marc, a grape residue from winemaking.

All we know is that something either in or on the grapes causes kidney damage. It reminds me of the mystery surrounding the kidney damage we see from dried meat treats. 

The toxin has yet to be identified. We don’t know if it’s found naturally in the grape or whether it’s a fungus or chemical that coats the surface.

How Toxic Are Grapes To Dogs?

The puzzle at the heart of grape poisoning is why some dogs can eat a large amount and be unharmed, whereas others eat tiny amounts and die. There are reports of dogs eating a kilogram of raisins and being unaffected, or a handful of sultanas and dying.

These are the lower end of reported doses that caused illness:

Raisins & Sultanas	3g per kg bodyweight
Currants	8g per kg bodyweight
Grapes	20g per kg bodyweight

The lowest toxic dose ever recorded was 4 to 5 grapes in an 8.2 kg Dachshund. That dog survived with treatment.

When To Go To The Vet

If you know your dog has eaten grapes, you should go to a vet straight away to induce vomiting. If it’s at night, that means a trip to the emergency vet. They should be able to remove the majority and provide activated charcoal to mop up any that slipped through.

So how many grapes constitute an emergency? Using the Dachshund as a guide we can say that one grape or sultana for every 2kg of bodyweight is probably the worst case scenario. However, given the uncertainty, it’s recommended to go to the vet to have even a single grape vomited up.

After 2 hours have passed, most of the grapes will have left the stomach. However, grapes, sultanas and raisins seem to leave the stomach slowly so I would still be inducing vomiting for up to 24 hours. 

If you miss the chance, the earlier we start treatment, the better their chances. Therefore, visit your vet for a blood test to check for kidney damage. A normal result in a grape-exposed dog is shown here.

Signs Of Grape & Sultana Poisoning

The earliest and most reliable sign of serious toxicity is vomiting, typically starting within 24 hours. Other signs include:

• Diarrhoea
• Weakness & lethargy
• Not eating
• Blood in vomit or stools
• Neurological signs such as dullness and ataxia (wobby legs)

Sometimes you can see grapes, raisins or sultanas in the vomit or faeces.

If your dog starts vomiting, and there have been grapes around, don’t ‘see how he is in the morning’; visit a vet immediately. The same applies to other toxic causes of vomiting like Nurofen®.

After 24 hours, signs of acute renal failure are likely to appear in these dogs. This will most often just look like a dog that gets sicker and sicker. A blood test will easily show the extent of the problem and what needs to be done.

Treatment Of Grape Poisoning

If the grapes can be removed from the stomach quickly, there may be no need for further treatment. However, when kidney damage is suspected we should closely monitor these dogs via repeated blood testing.

Treatment is support of the kidneys until they recover. We use high rates of fluids to flush the toxins, and sometimes diuretics to encourage urine flow. Dogs that receive treatment early are more likely to survive.

Other treatment depends on the individual, such as replacement electrolytes, antiemetics or antacids. 

The prognosis for recovery is excellent if treated early. Acute kidney injury only occurs in around 5% of early-treated poisonings, and mortality rates are around 1%.

The hardest thing is prevention. Grapes always fall off bunches and most dogs pounce on them fast. Sultanas and raisins in baked goods are everywhere.

The best thing is to only carry and eat grapes in bowls or bags, and recognise the danger of fruitcakes and buns. There will always be the one that gets away but I hope this article helps you decide what to do when it does.

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here. The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.