Keep dogs chocolate free at Easter:

Authorities are urging pet owners to keep their canine friends healthy these Easter holidays by keeping them on the dog food.

Chocolate, even in small amounts, can be deadly for dogs, said Angela Thompson from the NSW Department of Primary Industries (NSW DPI).

"Chocolates are for the family and kids to enjoy these holidays, however, pet owners need to stay firm and not be tempted to give chocolate to their dogs and other pets," she said in a statement.

"Chocolate contains a natural compound called Theobromine which can affect dogs' nervous system, behaviour and heart.

"Even a medium-sized chocolate bar can be dangerous and large amounts can be fatal."

Ms Thompson said dogs start suffering from vomiting and diarrhoea up to four hours after ingesting chocolate.

Advanced symptoms such as seizures might not be seen until 24 hours later.

And it's not just dogs who can suffer from chocolate toxicity.

"While dogs are the most susceptible, the toxin has been known to affect or kill cats, birds, rodents and reptiles as well," Ms Thompson said.

"Most pet owners have well and truly got the message about the dangers of chocolate and it is often children who inadvertently left chocolate within reach of pets."

Ms Thompson said people should take their dogs to the vet immediately if they think it has eaten chocolate.