Are Acorns Poisonous to Dogs?

The toxic compounds in acorns:

• Gallotannins (tannic and gallic acid)
• Physical hazard: hard, pointed acorn can cause gastrointestinal obstruction or choking

If your dog ate acorns, watch for:

• •Vomiting
• •Diarrhea (occasionally bloody)
• •Abdominal pain
• •Loss of appetite
• •Lethargy / depression
• •Dehydration
• •Constipation followed by diarrhea
• •Frequent urination and discolored urine (in severe cases)
• •Jaundice (in severe cases)
• •Acorns can obstruct the digestive tract, causing a blockage
• •Rarely: liver and kidney injury/failure, and in extreme cases death

My dog ate one acorn — is that an emergency?

A single acorn is unlikely to cause serious poisoning in most dogs, but it is not risk-free. The main concerns are stomach upset from tannins and the physical risk of the hard acorn causing a choking incident or intestinal blockage, which matters most in small dogs and puppies. Watch for vomiting, diarrhea, loss of appetite, or straining, and contact your vet if any appear or if your dog is small.

Why are acorns toxic to dogs?

Acorns and all other parts of the oak tree (leaves, bark, buds) contain tannins, specifically gallotannins, which irritate the gastrointestinal tract and can, in larger amounts, damage the liver and kidneys. Immature green acorns and red-oak acorns have the highest tannin levels. Acorns also pose a non-chemical danger: their hard, pointed shells can lodge in the throat or gut.

Are some acorns more dangerous than others?

Yes. Unripe (green) acorns contain more tannins than mature brown ones, and acorns from red oak trees have roughly two to four times the tannins of white oak acorns. Smaller dogs are at greater risk because fewer acorns are needed to reach a harmful dose and because obstruction is more likely in a small digestive tract.

• ASPCA Animal Poison Control - Toxic and Non-Toxic Plants: Oak (Quercus species)
• American Kennel Club (AKC) - Can Dogs Eat Acorns and Other Tree Nuts?

Last updated 2026-06-25