We've got a nut allergy sufferer in our family, and while it's useful that it's been bought to people's attention (years ago I heard someone declare 'there's no such thing as a nut allergy, it's all in your mind), the histeria is just ridiculous and more about preventing litigation than it is protecting people.
If you have a nut allergy and actually took the writing on food packets seriously, you'd never eat anything. EVERYTHING states that they 'cannot guarantee nut free', therefore rendering the whole thing useless. Might as well put 'might kill you, but if it does it's not our fault.'