A water quality expert has confirmed drinking water has the potential to cause skin irritations in some people.

Professor Stuart Khan, Head of School of Civil Engineering at the University of Sydney, said it was possible water from the tap - even that which sits within Australian Drinking Water Guidelines - could cause skin irritations for some residents.

A thread on the Facebook page Dubbo Community Group had approximately 15 people claim they or their family members - many of them children - were getting itchy skin from Dubbo's tap water.

Kay Clark, who began the Facebook thread, said two of her grand-daughters were getting "welts" on their skin after bathing and they had "been quite itchy".

Her two-year-old granddaughter who lives nearby with her mother Shakira Russell - one of Kay's daughters - was getting welts on her torso and legs.

Kay's second grand-daughter, aged two-and-a-half - who was visiting from Queensland with her mum Gabrielle and stayed in an Airbnb across the other side of town - had a similar skin reaction.

Kay took her first granddaughter to the GP who reportedly confirmed it was possible the tap water was causing the skin to become itchy.

"We had some blood tests and allergy testing done because we were a bit concerned that it could have been food related or it could have been product related, even though things had not been changed [in her environment]," Kay said.

"We eradicated stuff in her diet to see if that made a difference, but then we came to the connection that every time she had a shower or a bath it would happen with her.

"Then we sought medical advice ... and they said, well, it's a big possibility [the water is to blame]."

Kay said the water didn't sell right, either: "It smells real sulphur-y."

Kay's daughter who visited from Queensland, Gabriella Clark, experienced the same thing with her two-and-a-half year old.

"My daughter's never had any skin issues before," Gabriella said.

"All of a sudden she started ... breaking out in a rash on every limb of her body."

She said she began boiling the water for her daughter's baths, and she hadn't "had a problem since doing that".

Professor Khan said there were some substances in drinking water that could cause skin irritations, particularly when algae was present in reservoirs.

However, he said the cases in which this had been proven were few, and often the skin irritation was caused by an allergic reaction to something else in the environment.

"There are many, many different types of algae ... that can grow in drinking water supplies, and they themselves can produce many thousands of different chemicals, and some of them can cause skin irritations to some people," Prof Khan told the Daily Liberal.

"It's quite unusual for drinking water to cause skin irritations, but it's certainly possible."

Even in water that met drinking water guidelines, the fact that it was safe to drink didn't rule out the possibility that it could irritate the skin, according to Prof Khan.

"Drinking water guidelines are largely risk based. We try and identify what sorts of contaminants might be present and we focus on monitoring and removing those particular contaminants," he said.

"But unless things have come up in a risk assessment, there's always a possibility that there could be naturally occurring chemical substances that aren't being identified and aren't being monitored."

Although, Professor Khan said it was unusual for drinking water to cause skin irritations, and "people often do attribute things to drinking water that have actually been caused by something else".

He said it was "almost never" the drinking water that was the culprit, and it the sauce of the adverse reaction was usually food or other sources.

However, if there were a known contaminant - such as blue-green algae - in a reservoir being drawn on for drinking water, then it would "increase the likelihood" the water was to blame.

On February 26, WaterNSW issued a red alert advisory for high levels of potentially toxic blue-green algae for Burrendong Dam. However, the water board advised the warning was for untreated water only.

Kay, Gabriella and Shakira had Dubbo Regional Council test the water at their respective residences and it came back as "within drinking water guidelines".

Council said it continually monitors and tests water quality throughout the treatment and reticulation system to ensure the water meets the guidelines.

"All recent water sampling test results have indicated Dubbo's water supply complies with the Australian Drinking Water Guidelines," a council spokesperson told the Daily Liberal.

"Customers must make their own enquiries and seek professional advice regarding health or medical concerns.

"The property owner is responsible for all internal plumbing and drainage within their property."

Council said it had adopted procedures for reporting and responding to water quality complaints.

"Residents with complaints about water quality can reported them to Council by phoning 02 6801 4000 or lodging their details via DRC&Me," they said.

"Following a lodgement Council will arrange for staff to attend the affected property within customer service levels and obtain a sample from the water meter. The sample is tested against parameters outlined in the Australian Drinking Water Guidelines."