Hi Ashley and welcome!
What kind of doctor did you take your daughter to? You need to see a good, board certified allergist who is very familiar with the diagnosis and treatment of food allergies. Allergy testing is not accurate, so you'll need a good doc to help you figure out what (if any) foods your child is really allergic to.
I'd suggest reading the posts in this thread by our active members - those with 1000s of posts - because they contain good information. I'd also suggest you check out this
Other foods/MFA/EE section of the board for posts about multiple food allergies (MFA) and corn. Soy and wheat also have their own sections.
Like I said earlier in this thread, you will not find a packaged food that is free from corn, soy and wheat - it's just about impossible. If she's really allergic to all three, you'll probably need to feed her whole, minimally processed foods like fresh produce, rice, fresh meat, etc. - basically anything that just has one ingredient. Beware, most seasonings will have corn in them, even table salt. Here's a link that might help you avoid corn ingredients
http://go.livecornfree.com/listRight now, pollen is really bad in many areas of the U.S., so it could be that your daughter is simply having reactions to that or it's making her system hyper aware so she reacts to things she would normally tolerate. Do you have her on a daily non-drowsy antihistamine?