The Beaumont Veterinary Group Botley said the two food items contain harmful ingredients that can be highly toxic to dogs.
Every year, thousands of dogs across the UK require emergency veterinary care after eating these foods, and the risk increases significantly during the holidays.
Chocolate contains a chemical called theobromine, similar to caffeine, which dogs cannot process properly.
Even small amounts of chocolate can cause serious illness for a dog.
Raisins, along with grapes and currants, are also dangerous and can lead to kidney failure if ingested.
Hannah Gardiner, head vet at Beaumont Veterinary Group Botley, said: “Dogs are opportunists when it comes to food.
“With so many tempting treats around the home, it’s easy for pets to get hold of something harmful.
“Prevention is always better than cure.”
Chocolate and raisins are common ingredients found in advent calendars, desserts, chocolate tubs, Christmas cake, Christmas pudding and mince pies.
This makes the festive period a particularly high-risk time for pets.
Dog owners are advised to keep such festive foods well out of reach.
Advent calendars should be hung on walls rather than placed on low surfaces, and chocolate tubs, sweet bowls and cakes should be stored on high shelves or countertops.
Dogs should never be given chocolate or raisins as a treat, no matter how small the amount.
Hannah Gardiner added: “Christmas should be a time of joy, not worry.
“By keeping harmful foods out of reach and acting quickly if an accident happens, owners can ensure their pets stay safe and healthy.”
If a dog eats any chocolate or raisins, owners are encouraged to call their vet immediately – even if the dog seems fine.
Symptoms of poisoning can take up to four hours to appear and may include vomiting, stomach pain, diarrhoea, muscle tremors, seizures, a fast heart rate, excessive drinking, drooling, unsteady walking and rapid breathing.
These signs indicate that urgent veterinary attention is needed.
The Beaumont Veterinary Group Botley provides emergency cover throughout the festive season.
They use a chocolate toxicity calculator to assess the level of risk based on the type and amount of chocolate consumed.
Treatment may involve inducing vomiting to remove toxins and monitoring the dog for up to 48 hours.
In most cases, dogs make a full recovery if treated promptly, but delays can lead to serious complications.
The Beaumont Veterinary Group Botley encourages clients to contact them and book an appointment if they have any concerns about their pet at any time.
Appointments can be booked by calling the practice or online at the Vet Collection website.
Dining and Cooking