Peeled and cooked potatoes are safe for dogs, but potatoes sometimes contain a chemical that is also found in nightshade. Potato skins, raw potatoes and any green potato matter, including parts of the fully grown plant, are risky for dogs to eat.
Solanine is a toxin found in nightshade and related plants, such as tomatoes and potatoes. In potatoes, the toxin is found in the green parts of the plant and close to the skin of the tuber, which is the part that humans harvest to eat. Cooking potatoes at 320 degrees Fahrenheit or higher destroys the toxin. Raw potatoes and potato peels are risky treats, as they may contain the toxin. Green potatoes, potato sprouts and above-ground parts of the plant especially are toxic and can cause vomiting, diarrhea and death.