The local authority for the Western Isles has issued a warning to residents after recent samples gathered at a Loch near Bragar on Lewis were found to contain blue-green algae.
The samples taken from Loch Ordais in South Bragar indicated the presence of the algae with warning notices placed near to the location as a precaution to warn of the dangers.
If consumed, water from the Loch or the algal scum can cause stomach upsets and lead to more serious health effects, including skin problems.
The algae, which is found throughout freshwaters in the UK and further afield, take on the appearance of paint when they form scums.
Adverse medical effects known to be attributed to contact of the algae include skin rashes, eye irritations, vomiting, diarrhoea, fever and pains in muscles and joints.
A Western Isles Council spokesman said: “It is a sensible precaution for you, your children and your animals to avoid contact with the scum and the water close to it.
“For further information, contact the Environmental Health Team of Comhairle Nan Eilean Siar on 01851 822 694.”
Toxic algae has also been known to have caused the deaths of livestock and dogs, with the treatment of water supplies undertaken to remove the harmful substance.