Grapes, raisins, currants and sultanas can all have serious consequences if eaten by dogs, whether cooked or not. But this answer is not as straightforward as it seems – or this would be a very short blog post! Why exactly raisins can induce serious illness, which dogs are affected and whether the amount eaten changes anything are all questions mired in uncertainty.

In this blog, (especially for Halloween!) we look at the available evidence to try and determine some clearer answers. For the purposes of this blog, we will refer to ‘raisins’; but please note that currants, sultanas and all forms of dried grape are included under that heading.

So, are they actually poisonous?

The short answer is a definite yes… but only to some dogs. There is strong evidence that raisin or grape ingestion in dogs (and possibly some other species, including cats and ferrets) can cause catastrophic kidney failure. However, it does not appear to affect every single dog.

It is not known exactly how raisins and grapes can cause the dog’s kidneys to fail. The onset of effect after eating is around 6-48 hours and the consequences can be deadly. The kidneys can go into full ‘anuric’ failure. This means the dog is producing no urine, the kidneys have completely stopped functioning. Understandably, this is an extremely serious condition.

Are all dogs affected, and how do I tell if my dog will be?

No, some dogs seem to be able to tolerate grapes and raisins with no ill effect. Breed, sex and size of dog does not appear to play a role, and veterinary surgeons and scientists have so far not discovered why! There are anecdotal reports of large dogs sadly dying of kidney failure after eating just a few raisins. Equally, there are contrasting reports of small and young dogs eating whole Christmas puddings with no ill effect at all!

There is currently no way of knowing if your dog will have problems after ingesting these items. Previous blood tests showing good kidney function does not offer protection. Eating them previously and not suffering kidney failure is also not a reliable sign that they will be okay if they manage to get at some again.

This lack of information also means we have no way of telling what proportion of the dog population is susceptible. The Veterinary Poisons Information Service (VPIS) is a 24/7 emergency advice service for vets with queries about potential poisonings in dogs and cats. Between August 1994 and September 2007, 180 cases of grape/raisin toxicity were recorded by this service. That does not seem a huge number, but only a percentage of cases will be reported to the VPIS. Of these 180 cases, 68 went on to develop symptoms (37%). The amount and type of raisins or grapes eaten varied, as did the amount, and seemed to have no bearing on whether symptoms developed.

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Based on this, it appears that although cases are not hugely frequent, a significant proportion of dogs will be affected if they eat any amount of these foods: whether raw or cooked into cakes, puddings etc.

What are the symptoms?

Initial symptoms occur 6-12 hours after eating and include:

  • Vomiting
  • Diarrhoea
  • Excessive dribbling
  • Lethargy, weakness, quiet/dull demeanour
  • Abdominal (tummy) pain
  • Tremors
  • Dehydration, passing less urine than usual

This then progresses on into kidney failure:

  • Not passing urine at all
  • Severe vomiting and diarrhoea, sometimes bloody
  • Seizures
  • Coma

Can it be treated?

The key to a successful outcome in these cases is getting your dog seen by a vet as swiftly as possible if you know they have eaten grapes or raisins. Timing is of the essence here, so call your vet immediately, even if it is 3AM on Christmas morning!

If your dog is seen within a few hours of eating, it is likely your vet will make them sick to bring up any material before it has time to digest and start causing toxicity. Gastric lavage (flushing the stomach out via a tube) may also be needed.

Blood tests and urine samples may be required to keep a careful watch on your dog’s kidney parameters. Some cases will need hospitalising on fluid therapy to support and flush the kidneys or medicating to try and manage the effects of the toxins on the body.

Sadly, if the kidneys go into failure, or are already severely affected when seen, a high proportion of these cases will not survive.

If some dogs are immune, and my dog only ate a couple of grapes, do I still need to be seen?

Unfortunately, we have no way of telling which dogs can eat grapes and raisins without issue, and which dogs will suffer consequences. It also seems to be irrelevant how many they eat, or whether they are cooked or not.

Therefore, we would always advise any dog who is suspected of eating grapes or raisins to be seen immediately. That includes currant buns, Christmas pudding and cake, fruits scones…. anything which may contain grapes, raisins, sultanas or currants in either cooked or original forms.

When it comes to our pet’s health, “better safe than sorry” is a good mantra to go by. With such an unpredictable disease, prevention is the safest way to go: keep any foodstuffs involving grapes or raisins well hidden away, and if you think your dog may have eaten any then call your vet straight away.

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References

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