The tropical nut is chewed widely across South-East Asia and the Pacific and often mixed with lime powder (calcium hydroxide) to produce an addictive paste that stains the teeth and mouth a vibrant red.

It can also cause bad breath, tooth wear, gum recession, bleeding gums, and mouth cancer in regular users.

Ms Groves stopped selling betel nut when authorities cracked down on the product in Cairns, but said regulations had resulted in a booming black market for the product.

"[People] now just sell it at home," she said.

The Queensland Police Service said one person had been charged for possessing betel nut in 2019.

Australian Dental Association oral medicine specialist Professor Michael McCullough said the product was readily available in Melbourne where dentists are reporting a large increase in the number of concerning presentations associated with the product.

"Twenty years ago we were probably seeing only one or two of these changes associated with the use of betel quid and now we're seeing in Melbourne 30 to 40 in the public system."

Across the rest of the country that figure is estimated to be as high as 100.

Professor McCullough said cases were mostly seen in people recently migrated from countries where betel nut is chewed traditionally, including India and Myanmar.

"It could become a big problem in Australia if the habit continues," Professor McCullough said.

Professor McCullough said betel nut chewers should be on the lookout for signs of oral cancer such as ulcers that do not heal, changes in mouth texture, and white patches of soft tissue that can not be rubbed away with a finger or cloth.

"If people present with it really late and it's already spread to lymph nodes, it's already actually spread from the mouth, then the prognosis can be not as good and often requires also radiotherapy and chemotherapy."

He said late presentations of oral cancer could lower the five-year survival rate from 85 to 40 per cent.

He said there was likely to be many more undiagnosed cases of oral cancer in migrant populations that find it difficult to access healthcare.

One of Australia's closest geographical neighbours, Papua New Guinea, has the world's highest rate of mouth cancer due to the prevalence of betel nut chewing.

Internationally acclaimed Papua New Guinean musician George Telek nearly lost his singing ability when he suffered the disease in 2018.

Papua New Guinean woman Mary Scott said she had been chewing betel nut her entire life but was hesitant to visit a dentist when she moved to Cairns in 2000.

"My teeth have gone really bad. They've gone really short," she said.

She said more awareness was needed around the health risks of the product.

But market stallholder Ms Groves said it was unfair to ban betel nut while tobacco, a leading cause of oral cancer in Australia, was legal.

Professor McCullough said there was far more awareness about the health impacts and addictive properties of nicotine compared to betel nut.

"I don't think there's really the resources that are out there to help [people quit betel nut]," he said.

He urged people who use the product to see a dentist urgently and to stop chewing the product.

"It is very concerning. If [the trend] does continue we think it will compound the rise in cases of oral cancer in Australia," he said.