How do I help my 2yr old deal with his new found peanut allergy?

I gave my son one bite of bread with a very thin smear of peanut butter. Won us a trip to the ER. He got a bad case of hives. His eyes and ears were swollen. He went to an allergist and tested pos. for peanut allergy. Next week we'll blood test to rule out tree nuts. My dilemma is if it's not mandatory for manufactures to list products made in a peanut facility how seriously should I take this? We now have an EPI pen. If somehow he is introduced to a food that's made in the same factory as peanuts could this possibly build his immunity and help him outgrow the allergy. Or should I just take extreme measures and create a peanut free bubble for my son. DOES ANYONE WITH A PEANUT ALLERGY HAVE ANY ADVISE?