How is an accurate diagnosis made?
To make a diagnosis, allergists ask detailed questions about your medical history and your symptoms. Be prepared to answer questions about:
What and how much you ate
How long it took for symptoms to develop
What symptoms you experienced and how long they lasted
After taking your history, your allergist may order skin tests and/or blood tests, which indicates whether food-specific immunoglobulin E (IgE) antibodies are present in your body:
With a skin-prick test, a liquid containing a tiny amount of the food allergen is placed on the skin of your arm or back. Your skin is pricked with a small, sterile probe, allowing the liquid to seep under the skin. The test, which isn’t painful but can be uncomfortable, is considered positive if a wheal (resembling the bump from a mosquito bite) develops.
Blood tests, which are a bit less exact than skin tests, measure the amount of IgE antibody to the specific food(s) being tested. Results are typically available in about a week and are reported as a numerical value.
Your allergist will use the results of these tests in making a diagnosis. A positive result does not necessarily indicate that there is an allergy, though a negative result is useful in ruling one out. Skin tests alone are not considered enough to diagnose a food allergy.