The couple who ‘cured the common cold’ slammed by Shark Tank judges after one question.

A couple and their product have been slammed on Shark Tank after the sharks failed to see how an all-natural cold and flu medication could be worth a $1.5 million investment.

Husband and wife team Nicole and Steve Jones were confident when they walked in to meet the sharks on Tuesday night’s episode.

“Flu Away 48 is a 100 per cent all-natural medication that has been clinically proven to eliminate the symptoms of the cold and flu within 48 hours or your money back,” Nicole explained.

After clarifying that their product was essentially meant to “cure” the common cold using ingredients including garlic, echinacea and vitamin C, the sharks began questioning the couple’s request for a $1.5 million investment for a 20 per cent stake, valuing their business at $7.5 million.

There were a few raised eyebrows, but everything was seemingly going fine - until shark Dr Glen Richards enquired about the science.

"How do you think this works in the body? What exactly does it do to your immune system," the veterinary surgeon and entrepreneur asked.

It was a "good question" that the couple couldn't answer, turning Glen off on the spot.

"I really hope that's real," he said, when later making his final rejection. "There are so many people flushing serious money down a toilet. And I am concerned you're asking me to hoodwink the Australian public.

"The most that this is gonna do, super refined garlic will scare off a whole bunch of vampires and zombies, and this shark, so I'm out."

However, the other sharks were more interested in how exactly the couple arrived at their "$90 million in sales" projection and what it was they were buying.

Nicole and Steve clarified they were the worldwide distributor for the product, not the manufacturer, and they had so far invested $100,000 of their own money into the business.

This, more than anything, seemed to annoy Boost Juice founder Janine Allis.

"Why on earth did you come today and ask for $1.5 million, then? Why didn't you come in and ask for $200,000 or $100,000? 1.5 (million dollars) is cocky. Telling us $90 million in sales is cocky," she told the pair.

Janine wasn't having any of it when Steve started to defend his asking price, and say his profit projections were "conservative".

"[$200,000] is not what you need, it's what it's worth. You're saying, 'I need this money', because you do. You need that money to do it."

"Look, I tell you what. It's probably no surprise you know where I am. I'm sorry your previous business hasn't worked but you need to understand that you need to respect an investor and you need to not just throw numbers out that aren't justifiable."

Likewise, Andrew Banks, Steve Baxter and Naomi Simson had hesitations about the business and how profitable it could be, despite being assured it had been tested on 10,000 people, of whom 98 per cent said the product worked for them.

"Whether the product works or doesn't work, time will tell," Naomi said. "Today you've not demonstrated that you're sales and marketing experts in this field and for that reason, I'm out.