Could you explain serotonin syndrome to me?

Life: Threatening drug reaction to too much serotonin from one or several drug interactions, can cause neurological and cognitive symptoms.

Serotonin Syndrome: can occur when there is excess serotonin from serotonergic medications. Serotonin Syndrome can cause nausea /vomiting /diarrhea, abdominal pain, stiffness or spasm of muscles, fever, shivering, ^ sweating, hallucinations, confusion, visual changes, ^ Heart rate, tremor, lack of coordination, seizure, bp changes. In some cases, coma or death can occur.