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Food Allergies and Food Intolerance

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Differential Diagnoses For Food Allergies continued...

There are several other diseases that share symptoms with food allergies, including ulcers and cancers of the gastrointestinal tract. These disorders can be associated with vomiting, diarrhea, or cramping abdominal pain exacerbated by eating.

Gluten intolerance is associated with the disease called gluten-sensitive enteropathy or celiac disease. It is caused by an abnormal immune response to gluten, which is a component of wheat and some other grains.

Some people may have a food intolerance that has a psychological trigger. In selected cases, a careful psychiatric evaluation may identify an unpleasant event in that person's life, often during childhood, tied to eating a particular food. The eating of that food years later, even as an adult, is associated with a rush of unpleasant sensations that can resemble an allergic reaction to food.

Diagnosing Food Allergies

To diagnose a food allergy a doctor must first determine if the patient is having an adverse reaction to specific foods. This assessment is made with the help of a detailed patient history, the patient's diet diary, or an elimination diet.

The first of these techniques is the most valuable. The doctor sits down with the person suspected of having a food allergy and takes a history to determine if the facts are consistent with a food allergy. The doctor asks such questions as:

  • What was the timing of the reaction? Did the reaction come on quickly, usually within an hour after eating the food?
  • Was allergy treatment successful? (Antihistamines should relieve hives, for example, if they stem from a food allergy.)
  • Is the reaction always associated with a certain food?
  • Did anyone else get sick? For example, if the person has eaten fish contaminated with histamine, everyone who ate the fish should be sick. In an allergic reaction, however, only the person allergic to the fish becomes ill.
  • How much did the patient eat before experiencing a reaction? The severity of the patient's reaction is sometimes related to the amount of food the patient ate.
  • How was the food prepared? Some people will have a violent allergic reaction only to raw or undercooked fish. Complete cooking of the fish destroys those allergens in the fish to which they react. If the fish is cooked thoroughly, they can eat it with no allergic reaction.
  • Were other foods ingested at the same time of the allergic reaction? Some foods may delay digestion and thus delay the onset of the allergic reaction.

Sometimes a food allergy diagnosis cannot be made solely on the basis of history. In that case, the doctor may ask the patient to go back and keep a record of the contents of each meal and whether he or she had a reaction. This gives more detail from which the doctor and the patient can determine if there is consistency in the reactions.

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