Corn is special partly because it's everywhere. Being corn-free means eating almost no processed or pre-prepared food, and getting medications made without fillers by a compounding pharmacy. Most toothpastes, mouthwashes, cough syrup, etc. have corn. Some Tom's of Maine toothpastes are corn-free.
It's a lot of trouble! Too much for most people.
But, after my elimination diet in 2003, I got sick from a bowlful of corn. So I stopped eating large amounts of corn. I was addicted to fructose, which is made from corn, so I kept on using it even on the elimination diet. During 2003 I slowly tapered off on the fructose. After I'd quit, I got sick for days from a tablespoon of fructose. I was so startled I'd reacted to a trace - Brostoff and Gamlin's book on food intolerance said that people don't react to traces - that I tried it again. And I got sick for days again. So I quit fructose. But I was still using other corn-source products, like soy butter with maltodextrins, vanilla with corn syrup, and toothpaste with sorbitol. I was sick for 5 months solid in the summer of 2004. Then in the fall, I got sick from some time-release antibiotics. Time-release drugs all have corn gluten. So I tried to be REALLY corn-free for a week. Then I ate 1/16 of a grain of corn, and I got very sick for 5 days.
Then, I spent two months in bed, with back pain so bad I couldn't sit up more than a few seconds, severely woozy - as I slowly figured out that, ACTUALLY, I had intolerances to about 90% of the foods I'd thought were OK. I tried several things, but what worked was an elimination diet that cut out the top 20 food allergens. Then I felt better. I spent a lot of 2005 trying foods. I got sick from almost all of them. All of the top 20 food allergens that I've tried have made me sick for days.
So what corn did to me was not only to make me sick by itself - but also to mask a terrible underlying pattern of intolerances to almost all foods I'd been eating at all often. Lettuce, radishes and vanilla beans are the only foods I can eat that I used to eat often.
This probably happens to many people with corn - that they do an elimination diet and don't find any food intolerances, because they don't quit all corn. Because corn is (almost) ubiquitous.
This is a warning :)