my son allergic to soy, dairy, egg, peanut, tree nut and now apparently slightly to potatoe.
My advice? corn is the hardest. stay away from processed foods. good ol fruits, veggies, breads, bake your own breads, meats. oat meal. rice, noodles,
My husband was allergic to all above and corn and other things and ate a ton of veggies and sweet potatoes growing up. and pumpernickle bread for some reason.
cookies and all that stuff have corn syrup, that's gotta be really hard. but there's a ton of cookies and stuff you can make w/o it... just make a huge batch and freeze it.
and read labels. truely its not the end of the world when you get used to it. the issue is parties, school/daycare and being at other peoples homes. I have gotten very good at cooking eg: cupcakes w/frosting w/o egg or dairy and freezing them in case we have a birthday party or something to go to. but i've been doing this for almost 2 yrs!