Eleebana resident Bryson Andrew said he couldn’t figure out why he sometimes fell violently ill after eating prawns, while he was fine on other occasions.

That was until he discovered he was intolerant to sodium metabisulphite.

It’s a chemical the Food Standards authority allows prawns to be washed in to improve shelf life and prevent “blackspot” – where the shell becomes discoloured and is therefore visually unappealing.

And for people like Mr Andrew who are intolerant, the chemical can cause wheezing, nausea, pain and a skin rash or itch.

“No matter where you go I don’t see any sign on prawns to say whether there is any sodium metabisulphite present,” Mr Andrew said.

“It’s only once you put the pressure on and say you get sick if you eat it they’ll admit the prawns could have been washed in it.

“No wonder everyone’s having problems with all the chemicals in foods these days.”

Under the Food Standards Code uncooked crustaceans are allowed to have 100mg of sodium metabisulphite present per kilogram, while if they’re cooked they can have 30mg.

Because some people have bad reactions to the chemical, legislation requires a product with more than 10 parts per million to declare the use of sulphites on its labelling. 

“If the prawns are sold without a package or packaged in the present of the purchaser, which in most cases this is the way prawns are sold to the consumer, then they are exempt from labelling,” a Food Standards spokeswoman said.

“However, there is a mandatory requirement to either display the allergen information on or in connection with the display of the prawns or provide it to the purchaser upon request.”

Charlestown clinical immunologists and allergist, Dr Kathryn Patchett, said diagnosis of metabisulphite intolerance was done through looking at symptoms.

“There is no blood or skin test to diagnose such reactions,” she said.

“[Along with prawns] metabisulphites are also found in certain wines, beers and dried fruit.

“Avoidance is often necessary for patients who react to [such] food chemicals.

“Antihistimines and asthma puffers may help relieve symptoms.”

Hunter food service distributor  Red Funnel  supplies prawns to various pubs, clubs and businesses around the region.

Seafood manager Stephen Reah said if the prawns were green it was more likely they were dipped in sodium metabisulphite or another chemical but with cooked prawns it was “variable”.

“We buy our prawns frozen and it will depend on where the prawns are from as to whether they would have been dipped,” he said.

Mr Reah said  people who were intolerant to sodium metabisulphite should steer clear of prawns when eating out at restaurants.

“The majority of pubs and clubs don’t source from one supplier, they could have prawns from three different suppliers,” he said.

“You just wouldn’t eat them.”

Commercial Fishermen’s Co-operative Limited general manager Robert Gauta said he did not believe any Hunter-caught prawns were washed in chemicals.

However he conceded that at the moment local prawns only made up 20 to 30per cent of their stock at their Wickham store because not that many were being caught.

At their smaller shops in Swansea, Tacoma and Gorokan it was a bit better – around 70per cent, he said.

“There’s not so many local prawns around at the moment,” he said.

“At the moment a big percentage are being brought in from other areas.”

One of the outside areas Mr Gauta said prawns were coming from was Crystal Bay in Queensland.

Blue Harvest is the company selling the prawns from this area and managing director Sam Gordon said they were being washed in a product called Prawnfresh.

It is a sulphite-free option  that also stops blackspot, improves the prawn colour and increases shelf life.

Long-time Port Stephens prawn fisherman Geoff Sproule said he did not believe any Hunter-caught prawns were washed in chemicals.

He explained that they cooked the prawns on the boat, throwing them onto ice straight afterwards before sending them off to shops.

“The last I’d heard of any fishermen using metabisulphite around here was in 1976 with the Royal Red Prawns, which no one bothers with any more because they aren’t viable as they don’t get a good price,” he said.

 “We all wash the prawns in sea water, then cook them in sea water and they are then iced down or thrown into ice slurry straight away.

“My prawns are shipped off the boat every day.

“The trouble is everyone wants prawns around Christmas time but it’s not a great time of year to catch them around here.”