Has anyone ever had a blood test to screen for food allergies?

Yes: This is called "rast" testing. Though generally not as accurate as skin testing, blood allergy testing can be done in young children or in adults that are taking medications that would interfere with skin testing. It is also used in patients with skin problems that would prevent them from having skin testing.

See below: Blood testing to screen for food allergy is not the way to diagnose food allergy. Food allergy diagnosis is made by obtaining a history from the patient and making a decision that the story is c/w food allergy reaction. If the clinical story is appropriate then skin testing and / or food testing for food allergy can be done.

Not reliable: The gut has its own immune system to suppress immune reactions to foods; you can have a positive ige blood test to foods to which you don't react (false positive). Commonly available igg tests have no correlation with allergic reactions to foods. The best way to diagnose food allergies is to have an allergist take a comprehensive history of food-associated reactions, and do skin tests to confirm.