Cyanobacteria are a form of algae which can produce toxins harmful to the health of humans and animals exposed to or swallowing the water where the algae are growing.
Where cyanobacteria health warnings were in place, lakes should not be used for any activity that involved skin contact with the affected water, Vipond said.
"Swallowing water from lakes affected by blooms should also be avoided. Scums are a particular risk because they contain a high level of toxins.
"If contact with scum does occur, skin should be rinsed clean and clothing changed as soon as possible. This warning is particularly important for children."
He also sounded the alarm for dog owners - they should prevent their dogs from drinking or swimming in the water, as dogs were particularly sensitive to cyanobacteria.
"If people still choose to use the lakes when warnings are in place, or any other lake where there are visible changes to water colour, they should shower and change their clothing as soon as possible afterwards, even if no symptoms are noticeable."
Symptoms include a rash, skin and eye irritation; allergy symptoms such as hayfever and asthma; and possibly stomach upsets including diarrhoea and vomiting. Long-term exposure to cyanobacterial toxins may cause additional health risks.
Symptoms might not appear until some time after contact with the affected water, Vipond said.
The board's public health unit wants to hear from anyone who has suffered health problems after exposure to any of the Waikato lakes.
Health advice is available from the unit by calling (07) 838 2569.
Up-to-date information on cyanobacterial cell counts is available from local councils and Waikato Regional Council.
