How do you explain a positive antibody response to food(s) never eaten or consumed?

Cross contamination is very common. During daily living – eating out in restaurants, buying packaged/processed foods, having dinner at someone else's house, etc. – we encounter trace amounts of food proteins. This is especially likely when dining at restaurants where counters and food prep spaces have a variety of foods on them prior to your meal being served. Additionally, many food products contain the disclaimer "this food was processed in a facility that also processes nuts, dairy, wheat" which warns you the food item might be contaminated with trace amounts of other foods. Finally, we can get exposed to antigens via skin and inhalation. For example, you may breathe in wheat antigens while visiting a bakery. And many body care products contain food ingredients.