A Food allergy usually can be diagnosed with a thorough medical history taken by an allergist. The Doctor will want to know the following:
- When do symptoms occur? Food allergies typically cause symptoms with in a few minutes to several hours after exposure. Symptoms include stomach cramping, hives, lip swelling, runny nose, congestion and asthma. With a food intolerance, symptoms may not occur until the next day.
- How much did you eat? With food allergies, any exposure can trigger symptoms. For some patient, 1 mg - an amount that's almost impossible to see will provoke an allergic response. A reaction can even be triggered by kissing or sharing utensils with someone who has eaten a substance to which you are allergic. A skin reaction can occur from touching the substance. With a food intolerance, symptoms usually are linked to the amount consumed. Someone who's sensitive to milk, for example, can often drink a small amount without a reaction.
- Skin prick. Extracts of suspected foods are pricked into the skin with a needle. The appearance of a rash within a few hours or even a few minutes- indicate a food allergy. Caution: The skin prick test isn't advisable for patients with severe allergies. The tiny amounts of food used in the test could trigger a life threatening reaction.
- Radioallergosorbent test (RAST). This blood test detects antibodies to specific food proteins. The test occasionally produces false positive - indicating an allergy where none is present. It's often combined with the skin-prick test for more accurate results.