kimb
Have you gone to an allergy specialist? They can test you for food allergies. Also it may not be actual"lettuce" you are allergic to. If you were eating a salad with "wild greens" in it you could be allergic to Dandylion or some other type of green. It could also be something in the salad dressing...Like citrus??? At any rate you should find out exactly what it is because the 3rd reaction could be fatal considering that you may have already had an anyphalactic reaction!!