The paperwhite, also known as the daffodil or narcissus, is toxic to domestic dogs and many other mammal species, including humans. All parts of the plant contains a toxic alkaloid called lycorine. The bulbs are considered especially dangerous because they are easily confused with onions.
The alkaloid has a bitter taste and irritates the skin, creating a dermatological reaction known as lily rash. Symptoms of paperwhite poisoning include vomiting, excessive drooling and diarrhea, which progresses to trembling, convulsions and death if consumed in large quantities. The lethal dose for dogs is about 15 grams, or slightly less than ½ ounce of pure lycorine.