A FEW years ago most of us had never heard of the concept of gluten free food, now it is a multi-billion dollar industry.

It's become a whirlwind trend, transforming supermarket aisles and restaurant menus.

But for many, like Mark and his daughter Rebecca Mead, a gluten-free diet is the difference between being healthy or becoming very sick, very quickly.

The father and daughter have coeliac disease which means regular breads, breakfast cereals and snack foods are off the menu.

“I was quite sick through my teenage years,” Ms Mead said.

“Stomach bloating, not feeling well, iron deficient.”

Gluten is a sticky glue-like protein found in wheat and grains which people with coeliac disease can't process.

Consuming them makes them unwell and can stop their body from absorbing nutrients.

Ms Mead’s daughter Rosie was diagnosed with coeliac disease when she was two because she wasn't growing properly.

But not everyone who thinks they have the disease actually do.

But Dr Joe Kosterich said many simply have a sensitivity to gluten.

“A lot of these other people, they feel better, that's lovely, but a gluten sensitivity or intolerance is not a disease,” he said.

About one in 70 Australians have coeliac disease, but most of them don't know it. Research suggests that as many as 80 percent of coeliacs haven't been diagnosed.

A vaccine is being worked on and one is being trialled in Perth.

For now doctors say a blood test is the best place to start.