Grapes, Sultanas, and Raisins

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026
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Poisoning from grapes, sultanas, and raisins is a serious toxicological problem for pets, especially dogs and, more rarely, cats. This form of intoxication / poisoning is an acute poisoning caused by eating fruit of the grapevine (Vitis vinifera) or its dried products. The toxicity of these fruits for dogs was first scientifically documented in 1999, although the exact toxic substance has still not been fully identified. Notably, animals vary in their individual sensitivity—while some dogs develop severe symptoms after eating only a few grapes or raisins, others show no obvious signs of poisoning even after consuming larger amounts. This variability makes risk assessment difficult and makes preventive measures all the more important. Regardless of grape variety (red, green, seedless) or form of processing (fresh, dried, in baked goods), there is a risk of poisoning, which is why these foods are generally classified as highly toxic for dogs and cats.

The most important facts at a glance

Poisoning from grapes, raisins, and sultanas poses a serious threat to the health of dogs and, more rarely, cats. Despite intensive research, the exact toxic substance has not yet been identified. Toxicity is independent of grape variety or processing form and can cause severe signs of poisoning even in small amounts. Individual sensitivity varies considerably, making risk assessment difficult. The poisoning primarily manifests as acute nephrotoxicity, which can lead to life-threatening renal failure within a few days. Characteristic symptoms include gastrointestinal complaints such as Vomiting and Diarrhea, followed by signs of kidney dysfunction such as oliguria to anuria. Diagnosis is based on the medical history, clinical presentation, and laboratory findings indicating kidney damage. Therapy must be started immediately and includes decontamination, aggressive fluid therapy, and symptomatic treatment. The prognosis is favorable with early intervention, but worsens drastically once renal failure is established. Follow-up care requires long-term monitoring of kidney function. Prevention through strict avoidance of access to grapes and grape products remains the most important measure to protect pets.

Causes, development and progression

Grapes and their dried products can lead to poisoning symptoms in dogs even when relatively small amounts are consumed.
Not all dogs are equally sensitive.
Cats tend not to eat grapes, so they are not as much at risk.

Despite intensive research efforts, the exact mechanism of grape poisoning has not yet been fully clarified. The main cause of intoxication / poisoning is thought to be a substance-induced nephrotoxicity that can lead to acute renal failure. Scientific studies suggest that tannins, flavonoids, or certain mycotoxins may be responsible for the toxic effect. More recent studies have also considered tartaric acid as a potential trigger. The toxicity appears to be independent of the growing method, country of origin, or processing of the grapes. Even small amounts can cause severe signs of poisoning in sensitive animals. A critical dose is considered to be around 10–12 g of grapes or 2.8 g of raisins per kilogram of the animal’s body weight, although in individual cases significantly smaller amounts can also lead to poisoning symptoms. Individual sensitivity varies considerably, making it difficult to predict the risk of poisoning. Cats generally seem to be less at risk because they are less likely to voluntarily eat grapes and dried fruit; however, if they do ingest them, similar toxic effects are to be expected.

Mechanism of action

Renal insufficiency or renal failure is considered responsible for intoxication / poisoning caused by grapes or their dried products.
However, exactly how the kidneys are damaged is unknown.
In some animals, as little as 10–12 g/kg body weight of grapes or 2.8 g/kg body weight of raisins can cause signs of poisoning. Renal failure can occur within as little as 3 days.

Mechanism of Action of Poisoning by Grapes, Raisins, and Sultanas in Dogs and Cats

In dogs, poisoning from grapes, raisins, and sultanas is one of the most significant food-related intoxications / poisonings, with a potentially fatal outcome. In cats, the data are much more limited and poisoning cases are rarely documented—likely due to lower acceptance of these foods. The toxic principle has not yet been conclusively identified, but it is clear that even small amounts, especially in dogs, can lead to acute renal failure.

1. Affected Substances and Routes of Ingestion

  • Grapes (Vitis vinifera) – fresh, cooked, dried (e.g., in cake)
  • Raisins and Sultanas – dried grapes
  • Juice, baked goods, muesli bars—often contain hidden toxic amounts

Routes of Ingestion:

  • Direct oral ingestion (e.g., from the kitchen, table, trash)
  • Indirectly via prepared foods; pet owners often unknowingly give them as “healthy treats.”

2. Current findings on the toxic mechanism of action

Previously Unidentified Active Substance

  • Despite intensive toxicological research, the exact active substance has not yet been clearly identified
  • Hypotheses include:
    • Phenolic compounds or tannins
    • Mycotoxins on the fruit
    • Oxalic acid derivatives
    • Interactions with intestinal flora / gut microbiota or metabolism

Damage to the proximal tubules of the kidney

  • In sensitive dogs, there is direct tubular damage to the kidneys, especially the proximal tubules.
  • This likely occurs through:
    • oxidative stress
    • Disruption of mitochondrial functions
    • Calcium homeostasis disorders
  • The result is a sudden-onset, often irreversible acute renal failure (ARF).

Hypercalcemia as a Possible Consequence

  • In some cases, an increased calcium concentration in the blood is observed
  • Possible cause: tubular reabsorption dysfunction or disruption of calcium metabolism
  • Hypercalcemia itself may additionally contribute to tubular damage

3. Species Differences

Dog: Highly Sensitive

  • Dogs show individually very variable reactions
  • In some animals, even a few raisins (5–10 pieces) are enough to cause life-threatening symptoms
  • No clear correlation between dose and severity – idiosyncratic reaction is suspected

Cat: Rarely Documented Cases

  • Cats rarely ingest grapes and raisins voluntarily
  • Case reports exist, but no systematic poisoning data
  • Toxicity is not ruled out in principle, but appears to be significantly lower

4. Pathophysiological Changes

Target Structure Mechanism of Damage Consequence
Renal tubules (proximal) Cell damage due to oxidative stress and mitochondrial dysfunction Acute renal failure (anuria, azotemia)
Tubular reabsorption Calcium retention or release Hypercalcemia, secondary toxicity
GI mucosa Non-specific irritation or inflammation Vomiting, Diarrhea, Abdominal pain

5. Clinical Symptoms

Symptoms usually begin within 6–24 hours after ingestion, but can also appear delayed:

Early Phase (0–24 H):

  • Vomiting (usually multiple times)
  • Hypersalivation
  • apathy, inappetence
  • Abdominal pain
  • Diarrhea

Late Phase (24–72 H):

  • Azotemia (↑ urea, creatinine)
  • Oliguria to Anuria
  • Dehydration
  • Electrolyte imbalances
  • Lethargy, tremors, possibly Convulsions
  • Uremic coma

6. Summary of the toxic mechanism

Toxic Principle Consequences in Dogs
Nephrotoxic substance not yet identified Direct damage to the proximal tubules
Oxidative stress, mitochondrial damage Cell death, tubular necrosis
Hypercalcemia Worsening kidney damage, Cardiac arrhythmia
Idiosyncratic Reaction No reliable dose-response relationship

Conclusion

In dogs, poisoning from grapes, raisins, and sultanas causes acute, potentially fatal renal failure that can occur even with small amounts. The exact toxin is still unknown, but the toxic processes lead to irreversible tubular kidney damage. Cats are affected less often, but may also react sensitively. From a veterinary perspective: Even small amounts are considered dangerous, and any suspected ingestion requires immediate veterinary intervention.

 

Symptoms of intoxication

Symptoms usually appear 6–12 hours after raisin ingestion.

  • Vomiting
  • Bauchschmerzen
  • Weakness
  • anorexia
  • Diarrhea
  • Dehydration
  • increased thirst
  • Lethargy
  • painful abdomen
  • Tremor

Laboratory blood findings indicate worsening renal failure.
With complete renal failure, almost no urine is produced.
In most cases, the animals are then euthanized.

Clinical signs of poisoning from grapes or their dried products typically develop within 6–12 hours after ingestion. The first symptoms are often non-specific and include gastrointestinal complaints such as repeated Vomiting, which may often contain parts of the ingested grapes or raisins. Abdominal pain is indicated by a tense abdominal wall and pain responses on palpation of the abdomen. Affected animals also show lethargy, weakness, and anorexia. As the poisoning progresses, signs of dehydration and developing renal failure appear. These include increased thirst (polydipsia) with reduced or completely absent urine production (oliguria to anuria). In severe cases, tremors, ataxia, and neurological deficits may occur. The symptomatology reflects the progressive course of kidney damage, which can lead to complete renal failure within 24–72 hours after ingestion of the toxic substances. In cats, the symptomatology is similar, but fewer clinical cases are documented due to less frequent ingestion. The severity of symptoms does not always correlate with the amount ingested, underscoring the particular danger of this poisoning.

Diagnosis

Diagnosis of grape or raisin poisoning is based primarily on the medical history and clinical presentation. Key is confirmed or well-founded suspected ingestion of grapes, raisins, or sultanas, ideally with an estimate of the amount consumed. Laboratory testing includes a complete blood count, serum biochemistry with a particular focus on kidney parameters, and urinalysis. Characteristic bloodwork changes include elevated urea (BUN) and creatinine levels as indicators of impaired kidney function. Electrolyte testing can reveal disturbances in potassium, phosphate, and calcium balance. Urinalysis may show decreased urine concentration (isosthenuria), proteinuria, glucosuria, and the presence of casts as indications of tubular kidney damage. Imaging such as ultrasound may show enlarged, edematous kidneys with increased echogenicity of the renal parenchyma. In unclear cases, a kidney biopsy can demonstrate histopathological changes such as acute tubular necrosis. Because there is no specific toxin test for grape poisoning, the diagnosis is often presumptive, based on the combination of medical history, clinical presentation, and laboratory findings.

Therapeutic principles

There is no antidote.
Regardless of the (suspected) amount of grapes and grape products ingested, immediate, thorough decontamination is recommended in dogs due to the very wide variation in sensitivity and the very high toxicity for some animals, using emetics (medications to induce Vomiting) and repeated administration of activated charcoal.
As symptomatic therapy, intensive intravenous infusion therapy is given for 2 to 3 days. Kidney function should be monitored repeatedly at intervals.
If urine production decreases, an attempt should be made to increase renal blood flow using dopamine infusions.

Treating poisoning from grapes or dried fruit requires rapid and consistent therapeutic action. Decontamination is the priority if ingestion occurred less than 4–6 hours ago. Under veterinary supervision, Vomiting is induced, typically by administering apomorphine in dogs or xylazine in cats. This is followed by repeated administration of activated charcoal (1–4 g/kg body weight every 4–6 hours for 24 hours) to reduce absorption of remaining toxins in the gastrointestinal tract. Fluid therapy is the backbone of treatment and should be started immediately. Aggressive intravenous infusion therapy with crystalloid solutions (60–90 ml/kg/day) helps maintain renal perfusion and promote diuresis. Fluid administration is continuously adjusted based on hydration status, urine output, and kidney parameters. In cases of oliguria or anuria, diuretics such as furosemide or mannitol can be used to stimulate urine production. In severe cases, a low-dose dopamine infusion (1–3 μg/kg/min) may help improve renal blood flow. Symptomatic therapy includes antiemetics such as maropitant or ondansetron for Vomiting, gastric protectants such as omeprazole for gastric irritation, and analgesics for Pain. In advanced renal failure, hemodialysis or peritoneal dialysis can be life-saving, but is not available everywhere. Monitoring kidney function through regular checks of urea, creatinine, electrolytes, and urine output is essential for guiding therapy.

Prognosis & follow-up care

The prognosis for poisoning from grapes or dried fruit depends largely on how quickly therapy is started, the amount ingested, and the animal’s individual sensitivity. With early intervention within the first 4–6 hours after ingestion and successful decontamination, the prognosis is usually good. Animals that have already developed signs of acute renal failure have a significantly worse prognosis. Studies show that the mortality rate with established renal failure can be 50–75% despite intensive therapy. Follow-up care includes regular checks of kidney function over several weeks to months. Initially, kidney parameters should be checked every 24–48 hours; later, the intervals can be extended if progress is positive. A kidney-supportive diet with reduced protein and phosphorus content can be helpful during recovery. Animals that have survived grape poisoning should be monitored regularly for life for signs of chronic renal insufficiency, as subclinical kidney damage may persist even after clinical recovery. Owners must be thoroughly informed about the need to strictly avoid re-exposure, as surviving a poisoning can increase the risk of more severe consequences if ingested again.

Research outlook

Current research into grape toxicity in pets is focusing on several promising areas. A main focus is identifying the specific toxic compound in grapes and raisins. Recent studies are investigating various hypotheses, including the possible role of tartaric acid, certain flavonoids, or mycotoxins as triggers of nephrotoxicity. Another research focus concerns genetic factors that could explain the differing sensitivity between animals. Researchers are working on developing genetic screening methods to identify particularly at-risk animals. In parallel, innovative therapeutic approaches are being explored, including specific antidotes or adsorbents that could neutralize toxic substances more effectively than conventional activated charcoal. Advances in renal replacement therapy, such as portable dialysis devices for veterinary use, could improve treatment options for severe renal failure. Epidemiological studies are also examining possible links between growing regions, pesticide use, and grape toxicity. Through international research collaborations and the use of modern analytical methods such as mass spectrometry and metabolomics, it is hoped that the toxic mechanism can be fully clarified in the near future, enabling more targeted prevention and treatment strategies.

Frequently asked questions (FAQs)

  1. How many grapes or raisins are dangerous for my dog?
    The toxic dose varies greatly between individual animals. As a guideline, around 10–12 g of grapes or 2.8 g of raisins per kilogram of body weight is used. However, in some dogs, significantly smaller amounts can already cause signs of poisoning. Therefore: Any ingestion of grapes or raisins should be considered potentially dangerous.
  2. Are certain dog breeds more susceptible to grape poisoning?
    So far, no clear breed predisposition has been demonstrated. Individual sensitivity does not appear to be breed-specific, but varies from animal to animal regardless of breed. However, smaller dogs may be at risk from smaller absolute amounts due to their lower body weight.
  3. Are cats as much at risk as dogs?
    Cats appear to be similarly sensitive to the toxic substances in principle, but ingest grapes or raisins less often due to their selective eating habits. Therefore, poisoning cases in cats are documented far less often, but should be treated with the same seriousness.
  4. Are grape seeds or skins particularly toxic?
    Based on current knowledge, all parts of the grape are potentially toxic. There is no evidence that seedless or peeled grapes are less dangerous. Grape juice and raisins used in baked goods also pose a risk.
  5. How quickly do I need to act if my pet has eaten grapes?
    Immediate action is crucial. Contact your veterinarian or a veterinary emergency clinic immediately, ideally within the first 1–2 hours after ingestion. The earlier decontamination is performed, the better the chances of preventing severe kidney damage.
  6. Can I induce Vomiting at home if my pet has eaten grapes?
    Self-medication is strongly discouraged. Vomiting should only be induced under veterinary guidance, as improper administration can lead to complications such as aspiration pneumonia. Instead, go to the veterinarian immediately.
  7. How is grape poisoning diagnosed?
    Diagnosis is based on the medical history (evidence of grape ingestion), clinical symptoms, and laboratory tests, especially kidney values. Since there is no specific toxin test, the combination of these factors is crucial for making the diagnosis.
  8. Can my pet survive grape poisoning?
    With early and intensive treatment, the prognosis is good. However, if acute renal failure has already occurred, the chances of survival decrease significantly. The prognosis depends largely on how quickly therapy is started and the animal’s individual response.
  9. Are there long-term consequences after surviving grape poisoning?
    Animals that survive grape poisoning may suffer permanent kidney damage that can lead to chronic renal insufficiency. Regular checks of kidney function are therefore important even after apparent recovery.
  10. What other foods are similarly dangerous for dogs and cats as grapes?
    In addition to grapes and raisins, there are other foods that are toxic to pets, including chocolate, macadamia nuts, onions, garlic, avocados, xylitol (in sugar-free products), and alcohol. Each of these substances can cause severe signs of poisoning.

Literature

  • Eubig, P. A., Brady, M. S., Gwaltney‐Brant, S. M., Khan, S. A., Mazzaferro, E. M., & Morrow, C. M. (2005). Acute renal failure in dogs after the ingestion of grapes or raisins: a retrospective evaluation of 43 dogs (1992–2002). Journal of veterinary internal medicine, 19(5), 663-674.
  • https://www.msdvetmanual.com/toxicology/food-hazards/raisins-and-grapes
  • Sutton, N. M., & Bates, N. (2021). Canine toxic ingestions: A review of the most common substances reported to the Veterinary Poisons Information Service. The Veterinary Journal, 272, 105658.
  • Piripi, F., Carmichael, N., Bates, N., & Dhanani, J. (2019). Grape and raisin toxicity in dogs: A retrospective case series from the Veterinary Poisons Information Service. Journal of Small Animal Practice, 60(10), 598-605.
  • Cordeiro, M., Drobatz, K. J., & Giger, U. (2020). Current understanding of grape and raisin toxicosis in dogs: A review. Journal of Veterinary Emergency and Critical Care, 30(2), 132-143.
  • Koenigshof, A. M., & Beal, M. W. (2022). Acute kidney injury in dogs and cats: Pathophysiology, diagnosis, and treatment strategies. Veterinary Clinics of North America: Small Animal Practice, 52(3), 669-689.
  • Schweighauser, A., & Francey, T. (2020). Extracorporeal blood purification techniques in small animals: Current status and future perspectives. Frontiers in Veterinary Science, 7, 587336.
  • Löwe G, Löwe O. Notfälle bei Hund und Katze – Ein tierärztlicher Ratgeber. 2. Auflage. Kreuztal: Kynos-Verlag. 2021; 208 p.