The public has been cautioned to avoid Lake Hood after the discovery of potentially toxic algae.

Health New Zealand Te Whatu Ora issued the warning after Dolichospermum, a type of planktonic cyanobacteria, was found in the lake.

It may look like green globules floating in the water, or scum on the surface.

Public health medicine specialist Dr Annabel Begg said the algae could cause a number of health issues, including “skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips.

“If you experience any of these symptoms, visit your doctor immediately and please let your doctor know if you have had contact with the lake water.”

Boiling water will not remove the toxin.

Shellfish and fish in the lake, or downstream of it, may have ingested the toxin and consuming them is not advised.

Pets which have come into contact with algae, and are shwouign signs of illness, should be taken to the vet immediately.