Parsley is an herb that is commonly used to add flavor to dishes. While it is generally considered safe, consuming large amounts of parsley can be toxic. Parsley contains a chemical called apiole, which can cause kidney damage and gastrointestinal problems if consumed in large quantities. Symptoms of parsley toxicity include vomiting, diarrhea, and abdominal pain. In severe cases, parsley toxicity can lead to death. If you think you or someone you know has consumed too much parsley, it is important to seek medical attention immediately.