Can dogs eat walnuts?

Walnuts that are old, damp or lying on the ground often grow moulds. Some of these produce tremorgenic mycotoxins, which affect the nervous system. Dogs can develop tremors, twitching, a high temperature and seizures, sometimes within a few hours. You cannot always see the mould on a walnut.

This is the main reason vets advise against walnuts.

Black walnut trees (Juglans nigra), common in North America and planted in parts of Europe, produce nuts with thick green hulls that rot into black mush. The hulls and nuts are especially likely to carry moulds, and black walnut wood shavings are known to be harmful to horses. Keep dogs away from fallen black walnuts.

Walnuts are about 65 percent fat, with roughly 13 calories per half. Their wrinkled shape and hard shell pieces can irritate the gut or cause a blockage in small dogs. A dog that cracks open whole walnuts may swallow sharp shell fragments too.

Walnut halves also turn up in brownies, banana bread and salads with blue cheese.

A single fresh, shelled walnut half from a newly opened bag is far less worrying than old or fallen nuts. Watch for vomiting or loose stools over the next day, and do not offer more. If you are unsure how old the nuts were or whether they were mouldy, call your vet.

Walnut trees drop nuts from September to November. Collect them regularly and dispose of them in a closed bin. Fence off the area if collection is not practical.