Officials in New Brunswick and Quebec are warning consumers about the hazards of eating raw or undercooked fiddleheads as the new ferns come into season.

New Brunswick’s chief medical officer of health, Dr. Eilish Cleary, said in a release Monday that related cases of temporary illness have been reported in the province periodically since 1994.

Quebec’s ministry of agriculture, food and fisheries (MAPAQ) said May 8 it also gets reports of periodic cases of illness, each time due to inadequate cooking.

The symptoms of such poisoning include nausea, vomiting and diarrhea, starting anywhere from 30 minutes to 12 hours after the ferns are consumed, MAPAQ said.

It’s not known exactly what causes the temporary illness, Cleary said, but Health Canada believes it’s most likely the result of an unidentified natural toxin present in the fiddlehead.

“People should always thoroughly wash and cook fiddleheads by boiling them for 15 minutes, or by steaming them for 10-12 minutes until tender, before eating them,” she said.

MAPAQ also advised consumers to avoid eating raw or sauteed fiddleheads.

“Fresh fiddleheads are a delicacy that has long been enjoyed by New Brunswick residents and visitors during the short fiddlehead season in late spring,” Cleary said. “It is important to take these food safety measures to be able to thoroughly enjoy them.”

MAPAQ also advised those who don’t have the expertise to harvest fiddleheads to instead buy them at a recognized market.

Those who harvest or prepare their own fiddleheads are advised to sort them, throw out any that have unravelled and shake the remaining ferns vigorously in a plastic bag to remove any brown scales. If the stem’s extremity is brown, cut it with a knife or scissors, MAPAQ said.