Corn

Corn (maize) is one of the most produced crops in the world and shows up in the food supply far beyond the cob: corn syrup, corn starch, dextrose, maltodextrin, cornmeal, polenta, tortillas, masa, and countless processed-food ingredients. Many "gluten-free" products substitute corn for wheat, so people who avoid one often eat more of the other.

For most people, corn is well tolerated and a useful source of carbohydrate and fiber, especially in its whole forms. But it does cause issues for a meaningful minority — through allergy, non-IgE sensitivity, or FODMAP-related fermentation. Symptoms range from digestive (bloating, gas, diarrhea) to skin (eczema flares) to airway (congestion) depending on the mechanism.

Allergy vs sensitivity

True IgE-mediated corn allergy is uncommon but well documented, with reactions ranging from mild to anaphylactic. More common is non-IgE corn sensitivity, which shows up as delayed digestive or skin symptoms and is harder to confirm with testing — usually identified by an elimination diet. Cross-reactivity with other grasses and pollens is reported.

Hidden in processed food

Corn-derived ingredients are pervasive: high-fructose corn syrup, modified food starch, dextrose, glucose syrup, caramel color, citric acid (often produced via corn fermentation), and many "natural flavors." If you suspect corn, a strict elimination requires reading labels carefully and likely cooking most meals from whole ingredients for the trial period.