Solanine levels in S. nigrum can be toxic. Children have died from poisoning after eating unripe berries. However, the plant is rarely fatal, with ripe berries causing symptoms of mild abdominal pains, vomiting, and diarrhea.
Poisoning symptoms are typically delayed for 6 to 12 hours after ingestion. Initial symptoms of toxicity include fever, sweating, vomiting, abdominal pain, diarrhea, confusion, and drowsiness. Death from ingesting large amounts of the plant results from cardiac arrhythmias and respiratory failure. Livestock have also been poisoned from nitrate toxicity by grazing the leaves of S. nigrum. All kinds of animals can be poisoned after ingesting nightshade, including cattle, sheep, poultry, and swine. However, in central Spain, the great bustard (Otis tarda) may act as a seed disperser of European black nightshade (Solanum nigrum). Black nightshade is highly variable, and poisonous plant experts advise to avoid eating the berries unless they are a known edible strain. The toxin levels may also be affected by the plant's growing conditions. The toxins in S. nigrum are most concentrated in the unripe green berries, and immature fruit should be treated as toxic. Most cases of suspected poisoning are due to consumption of leaves or unripe fruit.
There are ethnobotanical accounts of S. nigrum leaves and shoots being boiled as a vegetable with the cooking water being discarded and replaced several times to remove toxins.