According to the ASPCA and the Pet Poison Helpline, poinsettias are rarely poisonous to dogs, and their toxicity is often overrated. The Pet Poison Helpline says that poinsettias may cause vomiting and drooling in dogs and, infrequently, diarrhea.
The Pet Poison Helpline says that if a dog's skin comes into contact with the white and milky sap of a poinsettia, skin irritation can result, and eye contact may led to mild conjunctivitis. Symptoms normally go away on their own, and vet attention is warranted only in severe cases. The helpline says that lilies, mistletoe, holly and rosemary are far more poisonous.