AN 18-year-old who suffered a fatal allergic reaction after eating at burger chain Byron ordered an item that was not shown to contain buttermilk on the menu, an inquest has heard.

Owen Carey, who had an allergy to dairy, died following a visit to the Byron restaurant at the O2 Arena in Greenwich, London, while celebrating his birthday with his family.

He started to experience symptoms after leaving the restaurant before later collapsing outside the London Eye.

Mr Carey died at St Thomas' Hospital in central London on April 22 2017.

An inquest at Southwark Coroner's Court heard on Thursday that Mr Carey, of Crowborough in East Sussex, had ordered a skinny grilled chicken burger with no sauce from the restaurant.

But the inquest heard the menu did not show the item contained buttermilk.

Barrister Clodagh Bradley, who is representing Mr Carey's family, argued the omission could make a customer "believe" it was a plain chicken breast.

Aimee Leitner-Hopps, Byron's technical manager, who is responsible for ensuring teams are fully trained in food safety, said there were many component ingredients in dishes that were not elaborated on in the menu.

She said: "If you have an allergy you should be asking for information and the team would be able to provide that information in the allergy guide."

Coroner Briony Ballard asked why allergy information had been in the "fine print" on the back of the restaurant's menu from 2017.

Ms Bradley also suggested the information was "difficult to read", stating it was in "black print" against a blue background.

Ms Leitner-Hopps, said: "I think most businesses were taking the same approach that the customer would inform the restaurant about (their) allergies.

"We have had numerous local authority visits over the years," she said, adding the restaurant had "never been told" the wording was not clear enough or was too small.

She said since the incident, and following research showing one in 10 people aged 16 to 24 hides their allergies, staff now ask customers directly if they have any allergies or dietary requirements.

Ms Leitner-Hopps said all staff at the time received online allergen training, which required them to tick different sections, along with onsite training.

"It was apparent to me training available to the teams was sufficient," she said.

The inquest heard that when staff are informed about an allergy, they press a button that ensures the world "allergen" is highlighted on the order ticket, along with space for further details, she said.

Staff are then expected speak directly with the kitchen team to ensure the allergy information has been received.

Coroner Ms Ballard said she would not read the report of the restaurant's head chef as the "error" appeared to lie at the "point of ordering and not at the back of the house".