Are winter berries toxic?

The leaves, seeds, bark and berries are all toxic, though the greatest concentration of alkaloids are in the berries. The berries contain an alkaloid called Theobromine that is almost identical to the caffeine found in coffee and tea, according to the Nova Scotia Museum. Large quantities of Theobromine can cause symptoms similar to a "caffeine overdose," such as dizziness, nausea, diarrhea, stomach pain, an elevated pulse or drowsiness. All species of holly plants contain toxic alkaloids.

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