Hi, welcome to the forum, determination of the food you are allergic to, is one of the challenges which you need to pass through. The common existing food allergens are
Peanut flour,
peanut butter, Powdered egg white, Powdered/fresh milk Soy milk, soy flour Wheat breads, flour etc.
As allergic reactions are IgE mediated, blood tests will show increase in these levels secondary to a food allergy.