The family of a Lee boy who died after a severe allergic reaction to milk found in popcorn were "disappointed" to receive no conclusive answers from an inquest.
Talented ice hockey player Ruben Bousquet, 14, suffered a severe anaphylactic shock after eating popcorn at an Odeon cinema in Greenwich last April.
He died in hospital the following day.
The schoolboy was allergic to milk, soya and eggs - but had eaten popcorn from the same cinema for years without any problems.
Ruben, who played for the London Knightz ice hockey team, was watching a film with his father at the IMAX Odeon, on April 17, the inquest at Southwark Coroners Court heard.
At a previous hearing, it is said he started to feel unwell after consuming popcorn with a Fanta drink at around 8.30pm.
But the youngster had forgotten his EpiPen, so his father quickly drove him home to retrieve it.
Ruben's breathing was initially fine, but it worsened as they approached the family home in Lee, a 15-minute drive from the cinema.
He developed hives on his chest and began clenching at his throat, the hearing heard.
The popcorn supplier, Thomas Tucker, collapsed last September after growing into one of the UK's largest independent popcorn manufacturers and supplying 90 per cent of the cinema industry.
It was rescued from administration by former director Paul Gregg in a deal worth £590,000.
Senior Coroner Andrew Harris said he had adjourned the earlier hearing to gather evidence on where cross-contamination may have occurred at either the supplier or in the cinema itself.
He said: "There are theoretical risks in cross-contamination at every stage from point of manufacturing to the point of purchase.
"Thomas Tucker's own tests found no milk proteins in salt or sweet popcorn. It showed the risk of cross-contamination was low and controlled by segregated cleaning. "I cannot determine if this was the source of cross-contamination, and nor can I exclude it.
"At the cinema, chocolate was pre-wrapped, coffee was handled on a different counter, and staff are not allowed to drink tea or coffee.
"The chance of cross-contamination would only involve speculation. I cannot prove it was the source of cross-contamination, nor can I exclude it.
"Ruben was very sensitive to milk proteins. 0.2 micrograms was sufficient to cause an allergic reaction.
"A failure to carry out a risk assessment at Thomas Tucker may have contributed to his death, there may have been a source of cross-contamination.
"I cannot conclude the cinema has any bearing, given Ruben had been consuming the same product for years.
"The failure to use an EpiPen immediately would have contributed to his lack of survival.
"Ruben was under the impression it was free of allergens and had he asked staff then that is what they would have believed too."
Mr Harris said he will make a report to prevent future deaths, but the family requested two more weeks to respond.
Judith Bousquet, speaking virtually from home, said: "We are disappointed there is no sound conclusion that the popcorn was contaminated.
“We wanted to have closure on that."
Giving evidence, the Food Standards Agency asked the coroner to invite them to collaborate with the UK Research and Innovation Board on addressing the problem of flawed allergen analysis to support risk assessment and risk management of food allergens.
Summarising his findings, Mr Harris found Ruben died from acute anaphylaxis to cow's milk allergen from cross contamination of popcorn.
He added: "I'm deeply sorry the family does not have the closure they would have wished.
"I hope the prevention of future deaths report I have in mind will have some reassurance that future instances are dealt with properly and lessons are learned."
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