Fiddlehead fern can cause several medical conditions, including nausea, vomiting, and diarrhea when eaten raw or undercooked.
Fiddleheads are toxic if eaten raw because of the high levels of arsenic they contain.
When consumed over an extended period or with excessive amounts at one time, arsenic causes liver and kidney damage.
If cooked properly, fiddleheads can be enjoyed without the risk of side effects caused by arsenic.