Are grapes and raisins poisonous to dogs?

Most of us have grown up often having grapes and raisins, either on their own as a healthy snack or in desserts. So how could something so everyday, so familiar, be poisonous to dogs? The (highly frustrating) answer is, we don’t know exactly.

Several theories have been promoted, suspecting either a natural component of the grape (skin), a substance used on grapes/raisins during farming or commercial processing or an organism that grows on or within the fruit. None of these theories have been confirmed yet and it’s not clear if there’s only one toxin involved or several.

Raisins are thought to be more toxic than grapes since the drying process concentrates the toxin(s). Sultanas, being in fact a type of raisin, fit this category too. True currants (of the genus Ribes) are not toxic to dogs, fresh or dried. But sometimes the name ‘currants’ is incorrectly used for a type of raisin (belonging therefore to the grape genus, Vitis), something worth keeping in mind.

And while the exact substance in grapes or its mechanism of action has not yet been discovered, their effect is sadly well-known. Grapes and raisins can seriously affect some dogs’ kidneys, hampering their blood-filtering activity, sometimes up to complete kidney shut-down and death.

The use of ‘some dogs’ is intentional. The sensitivity to grapes and raisins is highly individual and varies a lot from dog to dog. Some dogs will not develop any signs of toxicity even after consuming a decent amount of them and some will be affected only after a few.

Together with the unknown toxic substance and the way it works, this variability is a great source of headache for vets. Often people will think or tell others “my (other) dog had lots of grapes or raisins in the past and did not have any problems” and while this can certainly be true, it is not necessarily true for the other dog. It could cost the latter dog’s life to assume so. Hence the gravity with which vets approach every grape or raisin ingestion in dogs.

How to recognise it? Symptoms of grape or raisin poisoning

If you have seen your dog eating grapes or raisins or something containing them, the next steps are straightforward (see below).

For the cases when ingestion has not been witnessed, here’s a few signs of grape and raisin toxicity you may see:

• poor appetite,

• increased drinking or urinating,

• a sharp, sour smell to their breath,

• excessive drooling,

• vomiting and/or diarrhoea (possibly with blood in it),

• weakness and incoordination,

• lethargy.

When to see your registered vet

Up until recently, ingestion of any number of grapes or raisins was considered dangerous to dogs. But based on the evidence collected from a large number of cases, the Veterinary Poisons Information Service concluded that ingestion of 1 single grape or raisin very rarely leads to toxic effects, therefore for such cases close monitoring of dogs at home is acceptable.

This advice is obviously valid only for cases where it is known with absolute 100% certainty that the dog has only had one single grape or raisin.

If you are not sure how many have been ingested, or your pet is showing any suspicious signs, they should be assessed by a vet. Contact your registered (out-of-hours) vet practice immediately for an emergency appointment.

What can the vet do? Treatment of grape or raisin poisoning

Depending on how long ago the grapes or raisins were ingested, making the dog vomit will get rid of most of those still in their stomach and prevent further absorption of toxins. The toxin absorption happens at a medium rate, but in dogs the stomach content is rapidly emptied into the gut from where it cannot be vomited anymore. Therefore, the best window of opportunity for this is approx 2-2.5 hours after ingestion.

Vets use a special substance that when injected under the skin, triggers vomiting in dogs (called an emetic), please do not attempt to induce vomiting at home, especially with salty water or salt, this could easily cause a salt toxicity and make the situation much worse.

The next step is to give the dog activated charcoal. As its name indicates, activated charcoal is a very active substance, readily binding to gut content. When given in cases of intoxications, it binds to the toxins and reduces their absorption from the gut.

Since this needs to be given at regular intervals for 24 hrs (while the food passes through the gut), you will probably get some at home to mix into your dog’s food. The activated charcoal for veterinary use is a black liquid or paste of a certain concentration. It is different from the charcoal tablets used in humans for gassy guts (don’t give those to your dog either). Your vet will calculate and tell you/mark on the label the right dose to give your dog.

Last, but not least, your vet will recommend taking some blood samples to check your dog’s kidney function.

The toxic effect on the kidneys is not seen that quickly and may take 24-48 hrs to become obvious in the blood biochemistry. But two samples, one at the first presentation and another 1-2 days later, are recommended, so that there’s a recent reference to compare the second sample against.

Pets that are known to have prior kidney issues (like chronic kidney disease of older dogs) or have had a lot of grapes or raisins might need to be hospitalised for 24-48 hours for more intensive treatment, like intravenous fluid therapy and medications that keep the kidneys well-perfused and reduce the risk of damage to them.

What you can do

Be careful with grapes and raisins, especially when given to children around dogs. They might leave them lying around or feed them to the dog on purpose.

Apply the same precautions with baked items that (may) contain raisins, such as fruit cake, mince pies and hot cross buns.

If you have any questions about dog, grapes and raisins, please us the button on this page to book an appointment with FirstVet and within 30 min one of our friendly vets will be happy to discuss them with you.