Can dogs eat walnuts?

Why

Ordinary English walnuts (the ones in a Christmas nut bowl) don't contain a poison that targets dogs. The problem is what they're made of. Walnuts are extremely rich in fat, and a sudden load of fat is one of the classic triggers for pancreatitis — inflammation of the pancreas, which is painful, can make a dog very unwell very quickly, and sometimes needs hospital care. Dogs who have had pancreatitis before, who are overweight, or who are on a low-fat diet for a reason are the ones most likely to be tipped over by a handful of nuts. Even in a robust dog, that much fat usually means a day or two of sickness and loose, greasy stools.

Then there's the shape. A whole walnut is hard, round and just the wrong size — dogs bolt them rather than chew, and they can lodge in the throat or further down the gut. Shells and shell fragments are worse: they don't break down, they have sharp edges, and they're a real cause of blockages, particularly in small dogs and in the enthusiastic hoovering type who eats first and thinks later.

Black walnuts are a different matter, and worth being blunt about. They come from a different tree, are usually found fallen under it in their thick green-then-black hulls, and vets treat them as genuinely toxic to dogs rather than merely fatty. Dogs who eat black walnuts or their hulls can become severely sick, weak, wobbly or tremory. Nothing about a black walnut is worth risking — don't offer them, and don't let your dog forage under the tree.

Mouldy walnuts are the other true emergency, and they catch people out because the dog usually finds them, not you. Nuts lying on damp ground — or forgotten at the back of a cupboard — can grow moulds that produce tremorgenic mycotoxins: toxins that act directly on the nervous system. Signs can come on fast, within a few hours, and look like twitching, tremors, staggering and, in bad cases, seizures. A walnut that looks a bit fusty, or one your dog dug out of the garden or the bin, is not a tummy-upset problem. It's a ring-the-vet-now problem.

How much is sensible?

There's no reason to feed walnuts at all — they offer a dog nothing they can't get more safely elsewhere, and they burn through the treat budget fast (treats should stay under roughly 10% of your dog's daily calories, and a few walnuts is a lot of fat for a small body). If your dog does hoover up a small piece of plain, fresh, shelled English walnut, that's a very different thing from a deliberate serving: a single kernel-sized piece in a healthy Labrador will most likely pass with nothing worse than a rumbly tummy, whereas the same piece in a terrier or a dachshund is a genuine choking and obstruction risk, and a small dog reaches a problematic fat load far sooner than a big one. What should never be given, in any amount, to any dog: black walnuts, anything still in its shell, anything mouldy or picked up off the ground, and salted, spiced, honey-roasted or chocolate-coated nuts.

Signs to watch for

• Sickness or diarrhoea within a few hours, often loose and greasy-looking
• Going off their food, unusually quiet or flat, licking their lips or drooling
• A painful tummy — hunched up, tense when you touch the belly, or stretching into a bowing 'praying' position
• Retching, gagging or repeatedly trying to be sick without bringing anything up, or straining with no poo coming (possible blockage)
• Muscle twitching, tremors, unsteady or drunk-looking walking, panting and overheating — this points to mould toxins and is an emergency
• Collapse or seizures

If your dog has had too much

If your dog has swiped a small piece of plain, fresh, shelled walnut and is otherwise well, you don't need to panic: keep fresh water down, hold off rich food for the rest of the day, and watch them closely for 24 to 48 hours — ring your vet if they're sick more than once, won't eat, seem sore, or go quiet and flat. Ring your vet straight away, without waiting to see what happens, if it was a black walnut, a mouldy walnut, anything picked up from under a tree or out of the bin, whole nuts in their shells, a large quantity, or if your dog is small, elderly, or has had pancreatitis before. Any twitching, tremors or wobbliness means an emergency vet or an animal poison line now, not in the morning. Have the details ready — which sort of walnut, roughly how much, and when — and don't try to make your dog vomit unless a vet specifically tells you to; doing it at home can do more harm than the nuts.

Serving tips

• Walnuts roll. A bowl on the coffee table, a dropped one under the worktop, or a nutcracker session on the sofa is how most dogs get them — keep nuts in a sealed cupboard and sweep up after yourself.
• If you have a walnut tree, autumn is the dangerous season: clear fallen nuts and hulls regularly, or fence the area off. Ground-fallen nuts are the ones most likely to be mouldy, and black walnut trees are the reason some gardens are a no-go for dogs entirely.
• Watch the baking. Coffee-and-walnut cake, brownies and banana bread often carry chocolate, raisins or a sugar-free sweetener too — the other ingredients are frequently more dangerous than the nut, so treat any 'my dog ate a slice' moment as a call to the vet.
• Bin bags and compost heaps are the classic source of mouldy nuts. A lidded, dog-proof bin does more for food safety than any amount of telling them off.

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