I was on a US flight a few years back where a lady demanded a gaurantee from both the GA and FA that nuts would not be present on the flight. The FA made an announcement that pax should not consume peanuts on the flight due to this. (US did not serve peanuts). The FA told the lady that she could not gaurantee a 100% peanut free zone...

I'm with others who find this thing to be a little out of control.

Inconveniencing a plane-full of pax seems a bit extreme and selfish when the person with the allergy can take simple precautions of their own. Wear a mask and do not consume the nuts. If the allergy is that severe, perhaps modification of transportation options should be considered.