It's thought Northlanders are taking note of a warning to not consume shellfish off it's west coast.

Only one person has been seen by health professionals believed to be suffering from shellfish poisoning since a warning was extended to Hokianga Harbour.

The affected area runs from Northland down the coast to south Taranaki.

Northland DHB's Dr Jose Ortega said there are serious illnesses that can come from eating toxic shellfish.

"The feeling of tickling around the mouth or the face, hands and feet and you might have some difficulty swallowing or even breathing."

He said it's not worth collecting shellfish because it cannot be eaten safely.

"People might think that well I collect these and I am cooking them with the hope that will make them safe, well it will not make them safe. The toxin is not effected by the heat."