What if my dog ate watermelon that had gone off?

Watermelon that has spoiled may have started fermenting and contain ethanol. Call your vet or the ASPCA Animal Poison Control Center on (888) 426-4435 right away. Symptoms of alcohol poisoning in dogs include vomiting, disorientation, weakness, slow breathing, and collapse. Do not wait for symptoms before calling.

NOT SAFEReviewed May 2026

Can Dogs Eat Fermented Watermelon? No - Alcohol Forms During Fermentation

Q: Can dogs eat fermented watermelon?

No. Fermentation produces ethanol from sugars in the fruit. Ethanol is toxic to dogs even at small doses, causing symptoms ranging from depression and disorientation to seizures and respiratory depression. Any visibly fermented watermelon (bubbling, sour smell, slimy texture) should never be offered.

Fermentation converts the natural sugars in watermelon to ethanol via yeast metabolism. Ethanol is alcohol, and alcohol is toxic to dogs. This applies whether the fermentation is deliberate (homemade ferments, watermelon kombucha trials) or accidental (watermelon left on the counter for several days in warm weather).

If your dog ate fermented watermelon, call your vet now

Alcohol toxicity in dogs is a documented veterinary emergency. ASPCA Animal Poison Control protocols call for prompt assessment. Do not wait for symptoms. Call (888) 426-4435 or your nearest emergency vet. Source: aspca.org/pet-care/animal-poison-control.

How to Tell If Watermelon Has Fermented

• Sour, yeasty, or alcoholic smell
• Visible bubbles in the flesh or juice
• Slimy or stringy texture
• Pink colour has dulled to brown or grey
• Mould visible on cut surfaces
• Watermelon has been at room temperature for more than 4 hours uncovered, or more than 24 hours in the fridge after cutting

Symptoms of Alcohol Poisoning in Dogs

Within 30 to 60 minutes

Mild disorientation, unsteady gait, drowsiness, gastrointestinal upset (vomiting, drooling)

1 to 4 hours

Worsening incoordination, weakness, low body temperature, slowed breathing, depression

4+ hours (severe)

Collapse, seizures, respiratory depression, coma. Veterinary emergency.

Other Fermented Watermelon Products to Avoid

Watermelon wine / hard seltzer / cocktails: Alcoholic. Never offer.
Watermelon kombucha: Contains residual alcohol from fermentation. Not safe for dogs.
Watermelon kimchi or pickles: Often heavily salted and may contain garlic, onion, or chilli. Not appropriate for dogs.
Watermelon vinegar: Acidic and can irritate the GI tract. Not recommended.

Safe Storage to Prevent Accidental Fermentation

Cut watermelon: refrigerate within 2 hours of cutting (1 hour if room temperature is above 25 C / 77 F).
Use within 3 days when refrigerated in an airtight container.
Freeze any leftover cubes you will not use within 3 days (see frozen watermelon protocol).
Compost or bin any watermelon showing the spoilage signs above.

Sources

ASPCA Animal Poison Control on alcohol toxicity: aspca.org
Pet Poison Helpline on alcohol: petpoisonhelpline.com/poison/alcohol
Merck Veterinary Manual on ethanol toxicity: merckvetmanual.com/toxicology

ASPCA: (888) 426-4435 Other emergencies Safe preparation