A toxic alkaloid, solanine, has been isolated from this group of plants. Toxicity of these plants varies depending upon maturity, environment and portion of plant ingested. The berries are the most toxic part and are more toxic when they have matured. The berries of both Carolina horsenettle and black nightshade are green when immature. However, horsenettle berries turn yellow when mature and nightshade berries become black.
Leaves are also toxic, but to a lesser degree.
All classes of livestock and humans have been poisoned. The acutely poisoned animal is characterized by irritation of the mouth and gastrointestinal lesions. In the chronic form, unthriftiness, jaundiced mucous membranes, abdominal dropsy and constipation have all been seen.