Owen Carey, who had a dairy allergy, suffered a fatal reaction after consuming grilled chicken coated in a buttermilk at Byron burger.
A coroner said the act was childish and thoughtless but not designed to cause serious harm.
Natasha Ednan-Laperouse, 15, died after she ate an artichoke, olive and tapenade baguette from Pret
More than half of allergy sufferers have had reactions due to contaminated food, according to a poll for law firm Slater and Gordon.
ITV News has written to every UK council asking them how many complaints about an allergic reaction they've had in the last three years.
Researchers found children not normally able to tolerate exposure to a tenth of a single peanut eventually coped with two whole peanuts.
They were told by Michael Gove that "he sees no reason why the new law could not be in place by the summer recess."
The customer had eaten a flatbread which was supposed to be dairy-free, but it contained a yoghurt which was found did contain dairy.