A health warning has been issued for Lake Rotoehu due to a bloom of potentially toxic blue-green algae.

'This health warning means that people should avoid any activity which results in contact with the lake water,” Medical Officer of Health for Toi Te Ora Public Health says Dr Jim Miller.

'With high levels of blue-green algae in the lake, activities such as swimming or water skiing could expose people to toxins,” says Dr Miller.

Contact with the blue-green algae can cause skin rashes, stomach upsets, and, in some cases, neurological effects such as tingling around the mouth, headaches, breathing difficulties and visual problems.

Contact with water or inhalation of droplets affected by blooms of blue-green algae can also cause asthma and hayfever attacks in some individuals.

'This current health warning reminds us of the importance of doing your own check on the water before you use it, watching out for algal blooms or other signs of possible changes in water quality before jumping in,” says Dr Miller.

'The Bay of Plenty and Lakes region is a big place with lots of opportunities for using the water, but look before you leap. If the water looks discoloured, smells unusual, or if there is scum or leathery mats of black or brown algae on the surface of lakes or on the beds of rivers, swim or play somewhere else and don't eat shellfish from the area.”

He says after rainfall, water is likely to be contaminated with animal faeces from rural and urban run-off.

"As a precaution, avoid swimming in rivers, streams, lakes or estuaries for two to three days after heavy or prolonged rainfall, even for sites that usually have good water quality.

'It is also best to avoid swimming and collecting shellfish near pipes or culverts which run down to a waterway, where stormwater is discharged, and near wharves and marinas.”

Choose a healthy spot to swim in, by checking the latest swimming suitability gradings and water sampling results from LAWA before you head out: https://www.lawa.org.nz/explore-data/swimming/.