Here are some tests that may be used to help diagnose multiple food allergies:
Trial food elimination
Suspected foods are removed from the diet to see if signs and symptoms of food allergy improve or go away. For infants, this can mean continuing to breastfeed while mom avoids suspected food(s) from her diet, or a change in formula.
Elimination may be followed by an oral food challenge to confirm that there is a food allergy.
Oral food challenge
Some of the suspected allergen is fed to the patient, often in the doctor's office for safety, to see if a reaction occurs. A food challenge is "open" if the parent and/or patient know what the food is. It is "blinded" if they don't know whether it's a safe food or the suspected allergen.
Some tests use a patient's blood to see if a food is likely to cause an allergic reaction.
Skin prick test
The skin is pricked to introduce a small amount of the potential antigen under the skin, where it is in close contact with the immune system.