Dogs should not eat pesto. Traditional pesto contains garlic and onion, which are toxic to dogs and can cause serious health issues like red blood cell damage, anemia, and gastrointestinal upset. Additionally, pesto is high in fat and salt, which can lead to pancreatitis, dehydration, vomiting, diarrhea, and weight gain in dogs. Even small amounts of pesto can pose risks, so it is best to avoid giving any pesto to dogs. If a dog accidentally eats pesto, especially in large quantities, it is important to contact a veterinarian immediately for advice. There are dog-safe pesto alternatives that avoid toxic ingredients like garlic and onion, and use safe herbs such as basil and parsley without added oils or salts, but classic pesto should be strictly avoided for dogs.