What is the consequence of consuming large quantities of lily of the valley?

Consuming large quantities of lily of the valley can lead to significant health risks primarily due to the presence of toxic compounds called cardiac glycosides, particularly convallatoxin. These substances can disrupt the normal functioning of the heart, leading to cardiac distress, which may manifest as irregular heartbeats, changes in blood pressure, or even heart failure in severe cases. Additionally, the ingestion of these toxic components can result in digestive issues, including nausea, vomiting, and diarrhea.

While some of the other options might sound plausible, they do not encompass the severe and immediate risks associated with the toxic effects of lily of the valley. Neurological enhancement or cognitive impairment are not typical consequences of the plant's consumption, nor are allergic reactions commonly resulting from it, especially in the context of large quantities. The primary and most critical consequences are clearly cardiac issues and gastrointestinal distress due to the toxins present in the plant.