A 'red alert' was issued by Water NSW on Christmas Eve for Lake Hume and the bloom is worsening at Bowna.

Alpine Council issued an alert yesterday for the Harrietville Dredge Hole.

Alpine mayor Sarah Nicholas said direct contact with blue-green algae could cause allergic reactions such as skin rashes or itchiness, sore eyes, ears and nose or if swallowed, gastroenteritis, nausea or vomiting.

"We strongly recommend that people avoid contact with the water at the Harrietville Dredge Hole and keep their pets out of the Dredge Hole until this bloom has been resolved," she said.

"People who come in to contact with contaminated water should wash immediately in fresh water and quickly seek medical advice if you are experiencing illness after contact with affected water.

"Visitors to the dredge hole can still enjoy other recreational activities such as bushwalking, boating and sightseeing.

"Pet owners, please keep your pets from drinking or having direct contact with contaminated water too, to keep them safe."

Cr Nicholas said water from the dredge hole should not be used for drinking, cooking or other domestic uses.

"Irrigators are encouraged to take extra care to avoid spray drift, the pooling of water and inhaling mist from blue-green algae affected water," she said.

IN OTHER NEWS:

The blue-green algae levels at the dredge hole are very high, and it is likely to be some weeks before levels are low enough for safe swimming.

Council will keep the community updated as the situation progresses.

Water NSW advises any fish caught should be cleaned and washed thoroughly in uncontaminated water and any internal organs disposed of before consumption.