The diagnosis whether a person is actually allergic to a food is conducted in several steps:
By performing skin and blood tests, your allergist will know whether you are sensitized to an allergen and may be able to tell you a certain probability of severe reactions. However, for determining whether you actually are allergic to the allergen, the allergist will need to conduct provocation tests, in which you ingest the actual allergen under strict supervision of the allergist. In case you have experienced severe reactions before to a certain allergen, this testing may not be necessary or possible.
From our experience as a patient organisation of now about 7 years, we strongly recommend you visit a certified allergist / pediatric allergist in case you suspect and/or have experienced severe allergic reactions. They are equipped with the lastest knowledge with respect to diagnosing the various allergies, can advise on options for therapies (if any) and such a diagnosis provides you with more security in your daily life.