Negligent allergen labeling

My son ate half a chocolate on a connecting flight. It was a Swissair chocolate. Since he has a nut allergy we checked the label and no mention of nuts was made. Within 5 minutes of eating the little chocolate he went into anaphylactic shock where his throat began to close. We couldn’t understand why as we had checked the label and only the following was stated: “Finest Swiss chocolate made with sustainable cocoa”. Only when I turned the wrapper inside out did I find the nut warning.

This is incredibly negligent and dangerous. Allergens need to be clearly marked on the outside of all packaging especially when crossing borders and transporting people of many languages and food allergies. He ended up in the emergency room in hospital where luckily the doctors were able to open his airways. I have contacted Swissair but have received no comment from them.