From wiki

Holly berries can cause vomiting and diarrhea. They are especially dangerous in cases involving accidental consumption by children attracted to the bright red berries.[32] Ingestion of over 20 berries may be fatal to children.[31][32]

Holly leaves, if eaten, might cause diarrhea, nausea, vomiting, and stomach and intestinal problems.[32]

Holly plants might be toxic to pets and livestock.[33]

Holly berries are fermented and distilled to produce an eau de vie.[35][36]

(Fruit brandy).