Ryan Park's wife Kara Lamond and friend left with burns in Fraternity Club's margarita incident

Kara Lamond and her female friend were served drinks rimmed with contaminated salt. They received injuries consistent with ingesting caustic soda.

They were rushed to Wollongong Hospital after a member of the public called an ambulance.

The women would have experienced immediate and significant pain, University of Wollongong's Dr Judy Morgan said.

"They certainly would have known that something was wrong ... it has quite an instant burning sensation," she said.

Read more: Illawarra slips into drought: Save water to avoid restrictions, authorities warn

Caustic soda can dissolve cell membranes and "literally eat a hole in the side of your esophagus".

"Significant burning can then lead to scarring longer-term, which obviously can then lead to longer-term health effects like decreased ability to swallow."

The incident occurred on Thursday, October 19. Ms Lamond and her friend have since been discharged from hospital. The Fraternity Club is still open for business.

The Fraternity Club said in a written statement on Sunday it was working with police and they "deeply regret this occurred".

Read more: $2.5m Barrack Point home sells after 50-plus years in same family

Mr Park declined to speak to the Mercury and a spokesman for his office issued a statement.

"We note that police have advised investigations are currently underway," the statement said.

"The family asks that their privacy be respected and will not make any further comment on this matter during this time."

The NSW Food Authority is continuing to investigate the incident and will report its findings to NSW Liquor and Gaming.

Sodium hydroxide (known as caustic soda) is not toxic, but it is highly corrosive.

It's found in many cleaning products, such as drain cleaner, and used in the production of soap and often found in chemical labs, Dr Morgan, a senior lecturer at UOW's School of Chemistry and Molecular Bioscience at the University of Wollongong said.

Anything over eight per cent sodium hydroxide can be corrosive and cause burns. Caustic soda granules are 100 per cent sodium hydroxide. The more concentrated the greater the effects.

Dr Morgan said sodium hydroxide and common table salt have a similar appearance.

Read more: Meet the main players in the Illawarra offshore wind zone

Compounding the health issues, sodium hydroxide is soluble when it comes into contact with water, so Ms Lamond's friend would be left with burnt lips, mouth, esophagus and stomach.

"As it dissolves it actually releases heat as well, so you get two different forms of burning," Dr Morgan said. "You get the burn from the base or the alkaline substance, and you can actually also get burning from the actual dissolution process or the dissolving of the substance, because that releases heat."

Due to natural acids in a person's stomach the sodium hydroxide would largely be neutralised there.

The Fraternity Club declined to comment on how the mix up occurred and what unfolded during the emergency, and referred the Mercury to its statement issued on Sunday.

"We take this incident very seriously and have engaged an independent work, health and safety organisation to review our processes and fine-tune staff training, to ensure it is not repeated," the statement said.

Good Times Only director Ben Abraham owns a number of hospitality venues across the Illawarra including the Howlin' Wolf, Dagwood Bar and Kitchen, The Prince Wollongong and The Iron Yampi, and said he was shocked by the mix-up.

"We do use some pretty hectic chemicals and it's super important to use them in a safe manner and avoid cross contamination," he said.

Good Times Only has chemical identification data sheets on display for staff so risks are known and understood.

Reading this on mobile web? Download our news app. It's faster, easier to read and we'll send you alerts for breaking news as it happens. Download in the Apple Store or Google Play.