But for more than a decade, the Mount Martha teen never had to use it, despite being diagnosed with a severe allergy to cows' milk, nuts and eggs when he was a baby.

So the last place his parents Gabrielle Catan and Simon Tate expected things to go wrong was in hospital, when Louis was admitted overnight to Frankston Hospital with asthma just over two years ago.

Louis, 13, suffered a fatal anaphylactic reaction in the children's ward after eating a "spoonful" of a breakfast of Weet-Bix and soy milk.

His death is believed to be the first fatality linked to food preparation at a Victorian hospital.

"Because he was in hospital, I thought the medical staff would know exactly how to take care of him," said Louis' mother, Ms Catan.

"I didn't felt like I needed to say anaphylaxis is a life-threatening condition."

The opening day of the coroner's inquest into Louis' death has raised serious questions about Frankston Hospital's procedures for patients with allergies, and also about the investigation that took place in the wake of the death.

Irene Fisher, the patient services assistant who was responsible for serving breakfast at the ward on the day of Louis' death, said that a whiteboard which normally detailed food allergies did not have Louis listed on it.

Mrs Fisher said she had instead been verbally told about the allergies by a nurse when she began her shift.

Louis was admitted to Frankston Hospital on October 22, 2015, after coming home from school with laboured breathing.

His mother said she had left the hospital early the next morning to let her son sleep, with firm instructions for the nurse about what he should eat when he woke up.

"I told her that the safest food for him for breakfast was Weet-Bix, because it is widely available, and soy milk and if he needed anything else, maybe fruit," Ms Catan said.

"I really thought about the safest, simplest food that he could have that was readily available."

However when Ms Catan called the hospital to check on her son later that morning she was told that he had complained of a tingling sensation in his mouth after eating breakfast.

Hours later he was dead - his heart had stopped after doctors administered anaesthetic to help him breathe.

Mrs Fisher has confirmed that she had supplied Louis with Weet-Bix, soy milk and a glass of water, but also revealed that she had also prepared him toast with packets of jam and butter.

The veteran hospital worker said she had walked into his room with the toast but found it filled with doctors.

Under questioning, she said she never would have given him the toast and butter without checking with the nurse first.

Mrs Fisher said later in the day she was asked to supply the soy milk that had been in the ward fridge to someone at the hospital, but could not remember who that person was.

"They wanted the milk to be analysed, that's what they said."

However Ms Catan said when they had met with the hospital the following year she had asked why the breakfast had not been retained for testing.

"We were just told 'Oh, we didn't know that it would go so wrong and he would die," she said.

Helen Hutchins, a ward nurse, said a new computer system has since been introduced at the hospital, where details about patient's allergies can be listed.

In an emotional statement before the inquest began, Louis' father said the family strongly believed the death should have never happened, and that there were failures in the medical treatment he received after eating the breakfast.

"He was in hospital, at a place where he should have been safe. Yet despite us providing clear and concise communications about his food allergies, he died," Mr Tate said.

"Our hope is that this inquest not only provides us with the many answers we need and deserve, but that it closely examines food safety and anaphylaxis management protocols at Frankston Hospital."

The inquest continues.