Food allergy testing is any procedure that is used to determine whether or not a patient has an allergy to a certain food. Some tests are more precise and safer than others, but each may be used if a less invasive test is not available or not safe to perform. In most cases, food allergy testing will begin with the patient giving a description of when symptoms first occurred and any changes to his or her diet during that time. This gives doctors an idea of where to begin testing.
The first type of food allergy testing involves scratching a surface of the skin and exposing it to a particular food to see if an allergic reaction results. Common reactions includes swelling or redness in the area, as well as itchiness and hives. This test is not frequently used in those with preexisting skin conditions like eczema, because results may not be accurate. People who are expected to have severe allergic reactions such as shortness of breath or swelling of the throat may also be excluded from the scratch test.
Radioallergosorbent (RAST) testing is another type of food allergy testing that may be done when the scratch test is not possible. This procedure involves taking a sample of the patient’s blood to test for certain antibodies that may be present when an allergic reaction has occurred. The would mean that the immune system is ready to create another reaction in the event that the food is ingested again. The RAST test is generally very accurate, but suspected causes of allergy symptoms may need to be known ahead of time.
Doctors may also do food allergy testing in which certain foods are eaten or avoided depending on the situation. An elimination diet, meaning a diet in which one type of food is off limits for a set period of time, is generally the first choice. If by eliminating a certain food a patient stops having symptoms, then the omitted food is usually the cause of symptoms. In some cases, when all other tests have not given an answer, an oral food challenge may be performed. This means that a patient eats certain foods and is then monitored to several hours to determine if a reaction has occurred.
All food allergy testing should be done in the presence of a trained medical professional, because if a severe reaction does occur, immediate emergency interventions may need to be taken. Severe allergic reactions can include a swelling of the tongue and lips, shortness of breath, dizziness, shock, and death. Medications, when provided promptly, are generally effective at preventing the most severe of these symptoms.