Q: I have a chocolate lab and am regularly guilty of giving him table food. One hour ago I let him nibble on my leftover fruit salad from breakfast. My dog ate 3 grapes, will he be okay? My boyfriend says that according to veterinarians, grapes are poisonous to dogs and will kill him, but he seems fine. Though my boyfriend claims he is going to die.
A: We don’t know what “veterinarians” your boyfriend is referencing, but to us this sounds like he’s making a mountain out of a molehill. We’re not saying that grapes being toxic to dogs is a myth, because they definitely are poisonous and can’t eat them. However, the potential side effects should not be exaggerated, especially for such a large breed like a Labrador.
How many grapes it takes to kill a dog is usually a high number. Based on research, for 9 out of the top 10 breeds, it will likely take more than 3 to cause kidney failure. See table below which calculates how many.
Healthy vs. harmful
With humans, this fruit is considered a superfood. The amount of antioxidants in white grapes is low, but red grapes are hailed for their resveratrol content (as well as having about 2x the antioxidants as white/green varieties). How can something so healthy be so dangerous for Fido or your feline friend?
Chances are at least once in your life – especially during your childhood – you were guilty of feeding dogs grapes and raisins under the kitchen table (one of us here at Superfoodly did that with a Shar Pei and Siberian Husky as a kid… thankfully known harm did not occur). You probably had no idea they were bad for them and guess what? No one did, or at least it wasn’t widely known until somewhat recently.
When things changed
The Animal Poison Control Center (APCC) at ASPCA received around 200 phone inquiries between January 2001 and August 2004 about canines who had ate grapes or raisins (1). However if you rewind back to the 90’s, very few would call for this issue. This topic was not on peoples’ minds, despite the fact that there was plenty of evidence back then to suggest they were poisonous.
Here was the turning point.
The APCC AnTox database keeps records for virtually all animal health conditions and diseases which are reported to the registry by veterinarians.
In 1989, a trend in the database started to become evident, showing a correlation between dogs who eat raisins or grapes and acute renal failure (kidney failure).
Unfortunately it wasn’t until much later – the early to mid 2000’s – when this topic started getting adequate awareness. ASPCA did a better job [finally!] at putting out press on the topic. In the summer 2002 volume of ASPCA’s “Animal Watch” publication, they ran a piece titled “The Wrath of Grapes” (2).
Mainstream media would pick up on stories like that and repeat them on the 5 o’clock news. Eventually, the word got out among the public that yes, grapes are bad for dogs, as well as cats, guinea pigs, rabbits, and hamsters.
Though not all our furry friend are affected, as it is said – at least for now – that grapes are safe for rats, raccoons, and many other mammals. You can feed chickens grapes if they’re seedless and reportedly they love ‘em. Likewise for many other types of pet birds.
If you were guilty of giving them to your pet Chihuahua a couple decades ago, don’t feel bad about it because the ignorance of the topic was not your fault.
The reason they are toxic
Why can’t a dog eat grapes, but a human can eat them as well as most other animals? What is in a grape that is poisonous to dogs? Would you believe that no one actually knows the answer! In fact, no one can conclusively say whether it’s a new problem that arose during the last 3 decades, or if it has always been a problem that was just never detected until computer analysis.
Some have wondered if it’s GMOs or pesticides, but that is highly unlikely, especially since dogs get sick regardless of the grape source; from the store, from your backyard, a California raisin, a European raisin, seedless or regular, conventional or organic grapes, all have been documented as being toxic. Every species and variety affects them, which includes some types of currants that are actually a type of black grape.
Since the cause of toxicity is not known, it remains unknown if heat/pasteurization from food processing changes it. For that reason, canines as well as cats should avoid all products containing this ingredient.
In addition to the fresh fruit, avoid grape jelly, juice, and fruit gummies (i.e. Welch’s concord grape fruit snacks). We shouldn’t have to say this last item, but in case there is some nut job out there giving wine to their Doberman Pinscher, please don’t do it!
The most plausible theories which have been proposed are:
Idiosyncratic reactions – This is not an allergy, but the effect can be somewhat similar. It’s when there is a rare and unpredictable reaction to a substance, which occurs upon the first time being exposed to it. The reaction is specific to the individual (in this case, a specific canine), and unlike an allergy, it can occur upon the very first exposure.
Nephrotoxic mycotoxins – These are toxins produced by fungus and molds. The nephrotoxicity refers to those which affect the kidney. While this theory remains possible, to date none have been found on grapes that demonstrate a link to dog poisoning symptoms.
Can you be allergic to grapes? In theory, yes, you can be allergic to the protein in any type of organic matter. You may not think of grapes as a source, but proteins – at least some – are in practically all living organisms.
One cup actually contains about 1 gram of protein, but even if it contained 1/100th of that amount, in theory it could still be enough to trigger an allergic reaction since sometimes it only takes an amount that is in parts per million. Grapes are gluten free so they are not a good comparison, but think of baked goods and cross contamination for those with severe Celiac disease. Those people might be affected by the tiniest amounts of gluten present, even when they’re in parts per million.
Are dogs allergic to grapes? No, or at least that’s not what’s responsible for the toxicity symptoms. The source of what’s causing an allergic reaction isn’t always simple to diagnose, but determining whether it’s an allergic reaction or not is relatively straightforward based on trademark symptoms and what can be seen under a microscope occurring on the cellular level. That’s not happening with dogs, so we can rule out the side effects as being from an allergy.
How many are safe?
Technically, none. As far as how many grapes can a dog eat before getting sick or hurt, there is no black and white answer. Just like humans, each is unique and will react differently.
For the most severe outcome of acute renal failure (kidney failure), the lowest documented toxic grape dose is 0.32 to 0.65 ounces of grapes per kilogram of body weight (3) (4).
How does that amount convert to number of grapes for different breeds of dogs? Using the low end of that dose (0.32 oz/kg), we made the calculations based off the following 4 assumptions:
1. How much does one grape weigh? 5 grams.
That’s according to the USDA National Nutrient Database. They report that 10 Thompson seedless grapes weigh 49 grams (4.9 grams each) (5). We rounded that up to 5 grams for one grape. We specifically chose Thompson since it is the most widely sold in the United States for eating (wine and juices often use other varieties).
A number of other sources, especially Q&A websites like Yahoo Answers and forums, often cite dramatically different numbers as to how much a grape weighs when discussing them in relation to dog toxicity. Since they base their calculations off their assumed weigh, they come up with dramatically different answers as to how many grapes until documented poisoning. Unfortunately, it appears most of those other sources are incorrect and making outright assumptions or mistakes with their conversion from grams to ounces.
2. We took the top 10 most popular dog breeds in America.
Popularity according to the American Kennel Club’s 2016 rankings (6).
3. For each breed’s weight, we took the lowest number in their weight range.
For all but one breed, we used the weight range reported in Wikipedia. We then based calculations off whatever the lowest number was from either gender. The female often weighs less and therefore, the lowest number was often from the female.
4. For safety, the number of grapes was always rounded down.
We rounded down even when the fractional amount was closer to the next higher number.
|Breed||Weight (lbs)||Weight (kg)||Number of Grapes
(for 0.32 oz. per kg body weight)
|1.||Labrador Retriever||55 to 80||25 to 36||45|
|2.||German Shepherd||49 to 88||22 to 40||40|
|3.||Golden Retriever||55 to 75||25 to 34||45|
|4.||Bulldog||40 to 50||18 to 23||32|
|5.||Beagle||20 to 25||9 to 11||16|
|6.||French Bulldog||16 to 25||7.3 to 11.3||13|
|7.||Yorkshire Terrier*||4 to 7||1.8||3|
|8.||Poodle (Standard)**||45 to 65||20 to 29||36|
|9.||Rottweiler||110 to 132||35 to 60||63|
|10.||Boxer||55 to 71||25 to 32||45|
|*excludes teacup Yorkies which weigh less than 4 lbs
**weight not provided by Wikipedia, other source used (7)
How many grapes can a dog eat safely? The answer is kind of like how much cyanide can you eat safely. Only zero is safe, because no serving size – neither small or large – has any benefits, only bad side effects are possible. Sure, you may not get sick or experience noticeable harm from a minuscule amount, but that does not make it safe.
“My dog ate grapes and is fine!” is something you may hear (or may even say yourself). But with all due respect, that is a very ignorant statement to make. As with most things in life, the time between a cause and the effect from it can be literally any amount of time.
It’s kind of like if someone bombarded your brain with radiation for a day and you had no side effects from it. Not today, not tomorrow, not even next year. Does that mean you are fine? Absolutely not! With the case of brain cancer, it may take 10 or 30 years for the tumor to develop (8). So think about it… someone could have cancer at age 40 for something that occurred at age 10, when a cell mutation began to run wild.
In the same way with grapes, even if there aren’t obvious symptoms of harm and the dog isn’t killed, there may be slow damage being done to the kidneys over time as you feed them to your pet. Or perhaps kidney function was reduced by a few percent from the one-time ingestion… not something that will make them sick now, but in their older years the impact may be felt.
My dog ate one grape should I worry? Most likely not, especially if it was a one-time thing and not a recurring event. The larger the dog, the less the single grape will effect it (since the unknown toxic substance will be spread out over a great body mass). A grape relative to a 50 lb pit full is not a big concern.
Now if you have a tiny puppy, especially a young Yorkshire Terrier or Shih Tzu, then yes that one grape will be a greater dosage relative to their body and therefore, it justifies worrying about. If you have an adult German Shepard, Labrador or Golden Retriever, those are all large breeds so the amount of fruit will be quite small relative to their body size.
To say it’s safe if those larger breeds ate 3 grapes (or 2, 4, 5, etc.) would be a misnomer, but it would be more likely that less harm would be experienced than a smaller breed eating that same number. How many grapes can kill a dog will also depend largely on individual physiology. There could be two dogs that are the same breed, weight, and age, and one may get sick from eating 10 grapes while the other doesn’t. Like humans, we’re all built differently inside.
If your definition of being okay or fine = not dead or not needing a trip to the veterinarian’s office, then yes, most likely one or two grapes is going to be “fine” or “okay” for your adult dog, if it’s a medium or large breed. It’s the toy dogs and small breeds which might not be fine, such as a Yorkie, Affenpinsche, Chinese Crested, Maltese, Pekingese, Pomeranian, Pug, Italian Greyhound, Japanese Chin, Havanese, Dachshund, Chihuahua, and Brussels Griffon.
What are the side effects?
We’ve stressed the fact that adverse reactions – with anything in life – are not always obvious or immediate. However if it’s severe poisoning which will cause kidney failure, noticeable symptoms will occur within hours after your dog consumes the grapes:
- Abnormal drinking or urination
- Lack of appetite
- Halitosis (unusually bad breath)
The acute renal failure will typically occur after several days, but those side effects may begin within the first few hours after ingestion.
What to do if your dog eats a grape or product containing them, like raisins or grape jelly, is a simple answer; call a veterinarian. Ultimately, only they are qualified to advise you on whether the amount is something to worry about and if treatment is recommended or not.
The vet may wish to use treatment options such as:
- Induced vomiting – It is important to do this as soon as possible, because of how fast food passes from the stomach to the intestines (and then vomiting will not be an effective option).
- Supportive care at an animal hospital, which may include aggressive IV fluid therapy.
- Monitoring of kidney functions, such as frequent BUN/creatinine testing.
- Activated charcoal
The ASPCA Animal Poison Control Center (APCC) hotline is open 24/7, every day of the year including during all holidays like Christmas, New Years, and Thanksgiving.
You can call them for advice if your dog, cat, or other pet ate grapes. They will charge a $65 phone consultation fee, billable to your credit or debit card. That phone number is (888) 426-4435.