Can dogs eat it?
Are acorns poisonous to dogs?
Last updated 23 September 2026 · How we write and check this
Short answer
Yes, acorns can be harmful to dogs. They contain tannins that can cause vomiting, diarrhea and belly pain, and eating large amounts may damage the kidneys. Their hard shells and caps can also cause blockages. Discourage your dog from eating acorns on autumn walks, and call your vet for advice if it eats any, especially a small dog or puppy.
How acorns affect dogs
Oak trees produce acorns rich in tannins and gallic acid. In dogs, these irritate the stomach and intestines. Some dogs show only mild stomach upset, but the effect depends on the dog's size and how many were eaten. Larger amounts can lead to repeated vomiting, diarrhea, sometimes with blood, and abdominal pain. Very large amounts have been linked to kidney damage.
Green, unripe acorns and oak leaves also contain tannins.
Blockage risk
Acorns are hard, about 2 to 3 cm (1 in) long, and their caps are rough. Swallowed whole, they can lodge in the intestine of a small dog. Puppies who play with and swallow acorns are particularly at risk.
Acorn caps and pieces of shell can also scratch the gums and throat.
Autumn and mast years
Acorns fall from September to November. In some years, known as mast years, oaks produce huge crops and the ground is carpeted with them. Vets often see more cases during these years.
Preventing acorn eating
Walk dogs on a lead under oak trees during autumn if they tend to scavenge. Practice a reliable leave it cue and reward generously for ignoring acorns. Rake up acorns in your garden, and consider a basket muzzle for determined scavengers, introduced gradually with treats.
Signs to watch
Watch for vomiting, diarrhea, straining, loss of appetite, lethargy, a tense belly or changes in drinking and urinating. Signs often appear within hours but may develop over a day or two.
Keep a note of roughly how many were eaten.
Key takeaways
- Acorns contain tannins that upset the gut and can affect the kidneys.
- They can cause blockages, especially in small dogs and puppies.
- Autumn and mast years bring the most cases.
- A leave it cue and lead walks under oaks help prevent problems.