The owner of a Perth cafe which allegedly sold a brownie containing marijuana to a family with young children has pleaded not guilty to two charges under the Food Act.

Key points: A family of four became unwell after eating at the Bada Bing Cafe in Woodlands

A family of four became unwell after eating at the Bada Bing Cafe in Woodlands The parents claim their children suffered hallucinations after eating a brownie

The parents claim their children suffered hallucinations after eating a brownie Hospital tests subsequently showed traces of marijuana in the children

Nathan Sharp, owner of the Bada Bing cafe in Woodlands, has been charged with two offences under section 18 of the Food Act, relating to selling unsuitable food.

The charges followed a complaint by the family, who say their five-year-old daughter and three-year-old son became sick after eating at the cafe.

The mother subsequently fell ill, while seeking treatment for her children at Perth Children's Hospital.

Nathan Sharp is the sole owner of Sharp Holdings WA, which owns Bada Bing cafe in the Perth suburb of Woodlands. ( ABC News: Jon Sambell )

She and her two children tested positive for tetrahydrocannabinol, known as THC — the psychoactive component of marijuana.

Her medical report notes the father also took a urine test which tested negative for "tetrahydrocannabinol and other cannabinoids".

Father feared a brain injury

The father, who when interviewed by the ABC asked his name not be used, said his daughter began behaving so strangely he feared she had sustained a brain injury.

"I sat her up on the bench, and she said 'Dad, my eyes are going' … she said 'everything's jumping', she said 'the walls are different colours, it's pink, it's blue'," he said.

"And then the last one, which really scared me actually, was: 'my vision's coming and going, I can't see anything'.

"At that point, the only thing I could think of was it was something going on with the brain, you know a bleed, or something really serious."

Cafe owner thanks community for support

Mr Sharp appeared in the Perth Magistrates court on Friday morning, supported by his wife.

He spoke briefly to reporters as he left court.

"I would just like to say thank you to the local community for their time over the last couple of weeks and their ongoing support," he said.

"We look forward to defending these charges in due course.

A family claims their children suffered hallucinations after eating a brownie laced with marijuana allegedly served by the cafe. ( ABC News: Marcus Alborn )

"I've just pled not guilty and we will let the system take its course."

Asked how the cafe was faring, he said business was "good" despite the allegations.

Mr Sharp will appear in court again in September, when a trial date may be set.