Dogs can eat tomatoes, but only ripe, red tomatoes in small amounts and moderation. Ripe tomatoes are generally safe and non-toxic to dogs, offering some nutrients like vitamins and antioxidants. However, dogs should never eat green, unripe tomatoes or any green parts of the tomato plant (such as leaves and stems) because these contain toxins called solanine and tomatine, which can be harmful or poisonous to dogs. Ingesting large amounts of these green parts can lead to tomato poisoning with symptoms like vomiting, diarrhea, weakness, and confusion. Tomatoes should be given only as an occasional treat, and any stems, leaves, or green parts must be avoided to prevent toxicity.