Check before you share
Look the food up before offering it. Some everyday human foods — grapes, raisins, chocolate, onions, garlic and anything containing xylitol — are on standard veterinary toxin lists.
Also check the whole product, not just the headline ingredient. A blueberry muffin is not a blueberry.
Start with a very small amount
Offer a single small piece and then wait. One new food at a time makes it obvious what caused a reaction.
Watch for vomiting, loose stools, gas, itching, or unusual behaviour over the following day.
When to stop and call your vet
Stop offering the food if your dog reacts badly, and contact your vet if symptoms are severe or last more than about a day.
Call your vet or an animal poison control service immediately if your dog ate something potentially toxic, regardless of whether symptoms have appeared.