New Delhi, Sept. 16 -- Owen Carey was finally 18, and a London burger joint on the River Thames seemed like a great place to celebrate.

The teenager opted for a grilled chicken breast. Just to be safe, Carey alerted staff at the branch of the Byron restaurant chain about his dairy allergy. It appeared he was satisfied with what he was told, and after ordering from a menu that made no mention of it, dug into a meal that had been marinated in buttermilk.

He got through a few bites. Then, his lips tingled. His stomach churned. After leaving the restaurant, he collapsed near the London Eye less than an hour later, the BBC reported. He later died in a hospital.

The 2017 incident sparked sadness and outrage among Carey's family members, who se...