Marigolds are considered mildly toxic to dogs. They are not highly poisonous but can cause mild irritation if ingested, affecting the gastrointestinal tract and potentially causing symptoms like vomiting, diarrhea, and stomach pain. Contact with the sap of marigolds may also cause skin irritation in dogs. However, marigolds are generally not a major cause for concern unless a dog consumes a large amount or has a specific sensitivity. It is best to prevent dogs from eating marigolds and monitor them for any symptoms if they do come into contact with the plant.