Can dogs eat blue cheese?

The detail

Blue cheese gets its flavour and its veining from Penicillium mould cultures deliberately introduced during production, and that same mould family produces a group of compounds called tremorgenic mycotoxins, including penitrem A and roquefortine C. A 2020 study testing 46 retail blue cheeses found roquefortine C in every single sample, with English Blue Stilton showing the highest average levels of any origin tested.

The veterinary picture on roquefortine C specifically is more nuanced than a lot of pet sites suggest. The MSD Veterinary Manual notes that roquefortine C on its own has shown limited tremorgenic activity in animal studies, and that many suspected roquefortine C poisoning cases were never tested for penitrem A, a much more potent tremorgen that is often produced alongside it by the same mould. In practice, a dog eating mould-affected dairy is rarely exposed to just one isolated toxin.

Real veterinary cases of tremorgenic mycotoxin poisoning in dogs are documented, and dairy products are named among the typical sources, alongside mouldy bread, nuts and compost. A published case report describes an eleven-year-old dog developing seizures, facial twitching and loss of coordination after raiding a compost pile, with penitrem A, roquefortine C and paxilline all confirmed in its vomit, which shows how these toxins commonly turn up together rather than alone.

On top of the mould question, blue cheese is one of the saltier, fattier cheeses on a UK cheeseboard, and a rich, fatty dairy food is also a plausible trigger for a bout of pancreatitis in a sensitive dog, quite apart from any mycotoxin risk. Between the mould, the salt and the fat, there is no good reason to offer it deliberately.

Is a small crumb of blue cheese actually dangerous?

A single small crumb dropped and hoovered up is unlikely to cause a dramatic reaction in most dogs, and the honest answer is that no dog-specific toxic dose for roquefortine C has been established. That is different from saying it is fine, since it simply means nobody has defined a safe amount.

The safer approach is to treat any blue cheese as something to keep away from a dog on purpose, the same way you would with an unknown mushroom, rather than deciding a small amount is a reasonable treat. If a dog does eat a larger piece, that is when to call your vet.

My dog ate a piece of Stilton, what should I do?

Call your vet, especially with Stilton specifically, since the 2020 cheese study found English Stilton carried the highest roquefortine C levels of any blue cheese origin tested, well above French, Italian or Danish varieties in the same sample set.

Watch for vomiting, drooling, tremors, twitching or unsteadiness over the following few hours, since the MSD Veterinary Manual notes tremorgenic mycotoxin signs can begin within one to two hours of ingestion. Do not wait for symptoms if a meaningful amount was eaten, ring your vet straight away.

Can dogs have Roquefort or Gorgonzola instead of Stilton?

The same caution applies to any blue-veined cheese, since Roquefort and Gorgonzola use closely related Penicillium mould strains to Stilton, and the 2020 study found measurable roquefortine C in French, Italian, Danish and Polish blue cheeses as well as English ones, just at somewhat lower average levels.

There is no blue cheese variety that avoids the mould entirely, since the veining and the flavour it creates are the same process that produces the mycotoxins. Treat all blue-veined cheeses the same way.

Is regular mouldy cheese as risky as blue cheese?

Any cheese that has gone off and grown unintended mould is a similar or greater risk, not a lesser one, since Pet Poison Helpline groups all moulded dairy products together as a mycotoxin risk, without distinguishing deliberately cultured blue cheese from cheese that has simply spoiled.

A block of cheddar with an unexpected patch of mould has not been through the controlled fermentation blue cheese uses, so it is not automatically safer, it is simply a different, less predictable source of the same broad problem. Bin any mouldy cheese rather than offering scraps to a dog.

Are plain cheeses like mozzarella or cheddar a safer swap?

Yes, plain, non-blue cheeses such as mild cheddar, mozzarella or a low-salt cottage cheese do not carry the mycotoxin risk, since they are not made with the same mould cultures. They still bring fat and, in many cases, salt, so a small amount remains the rule.

Watch out for lactose sensitivity too, since VCA Animal Hospitals' guidance on food intolerance in dogs notes that dogs vary in how much lactase they produce, and dairy can cause loose stools or wind even in dogs with no allergy at all.