Poison Sumac. Poison sumac, Toxicodendron vernix, is related to the poison ivies and poison oaks, not to the other sumacs. It is relatively rare, compared to the other members of the family. The rash-causing agent, urushiol, is the same, and it causes the same rashes.
Most symptoms relate to movement of the face and hands, although some variants on this disorder have different symptoms. Almost always, tardive dyskinesia symptoms involve involuntary movements of some kind. In variants of tardive dyskinesia, a person may feel driven to move but may be able to control movement for a while. Usually, tardive dyskinesia symptoms include mouth and hand movements, although the limbs may move as well. Making faces, such as grimacing or puckering the lips, is common. One distinctive movement is the constant chewing associated with this disorder. The tongue may also protrude or move in unusual ways.
Treatment with metoclopramide can cause tardive dyskinesia, a serious movement disorder that is often irreversible. The risk of developing tardive dyskinesia increases with duration of treatment and total cumulative dose. Metoclopramide therapy should be discontinued in patients who develop signs or symptoms of tardive dyskinesia. There is no known treatment for tardive dyskinesia.