Nightshade plants, of the Solanaceae family, include weeds, ornamental plants and many of the vegetables found in any kitchen. While ripe fruits, vegetables and berries from these plants are typically safe for human consumption, some fruits with green spots, stems and leaves contain solanine and other alkaloids, which are toxic to dogs.
Solanine is the toxic chemical found in nightshades, such as potatoes. The more a nightshade plant is exposed to sunlight and warm temperatures, the higher the solanine concentration. Solanine is a cholinesterase inhibitor that prevents the removal of acetylcholine from neuromuscular junctions. Buildup of acetylcholine in the tissues contributes to neurological symptoms.
Symptoms of nightshade poisoning include increased salivation, drooling, loss of appetite, stomach upset, diarrhea, drowsiness, confusion, changes in behavior, weakness, dilated pupils and a decreased heart rate.
Some common nightshade plants that are toxic to dogs include nightshade, European bittersweet, climbing nightshade and horse or bull nettle. Popular ornamental nightshade plants include petunias and angel’s trumpets. In your vegetable garden, nightshades include eggplants, tomatoes, potatoes and peppers. Potatoes are safe for your dog if there are no traces of green in the skin or the skin is removed. The leaves and peels are toxic. Ripe tomatoes are generally safe for dogs.