Allergy Testing & Therapies
ALLERGY TESTING & THERAPIES
An oral food challenge (OFC) is a supervised process in which a food is eaten slowly, in gradually increasing amounts, under medical supervision.OFC’s are usually done when a careful medical history and allergy tests, such as skin and blood tests, are inconclusive. The OFC is a more definitive test because it will show whether the food ingested produces no symptoms or triggers a reaction.
In clinical practice, most OFCs are performed openly, meaning that both the patient and the doctor administering the OFC know what food is being eaten.
In a blinded challenge, either the patient (single-blind), or both the patient and the medical personnel (double blind) do not know whether the test food being eaten is real or a fake food, known as placebo.
This is important as a double blind OFC is considered the most accurate OFC test available. Blinded challenges are rarely performed in clinical practices, and are usually done in research studies.
With an OFC, you need to be in good health on the day of the test. Chronic allergic conditions such as asthma, atopic dermatitis (eczema), and allergic rhinitis must be controlled. If you are sick on the day of the test, postpone it. You should also carry your usual medications and emergency medications with you so you have them for the trip to the doctor and back.
Antihistamines have to be stopped before the OFC since they might mask mild early symptoms. It may be difficult to stop allergy medications during an allergy season or in patients with significant eczema, therefore OFCs may need to be timed to avoid the seasons that cause problems.
Foods which are challenged depends on the patient. First, discuss your child’s food preferences. For infants, younger children, or picky eaters, you may need to have several food options ready to minimize the possibility of food refusal for a picky eater. In addition, certain food proteins can be tested via different foods (iesoy may be tested as edamame, tofu, soy ice cream, or soy milk).
You will be instructed to avoid food or have a very light meal before starting your challenge. A physical examination and vital signs are done before starting and every 15-30 during the test. The OFC starts with a small serving of the food and after a consistent interval of time, if no symptoms are present, a slightly larger amount is eaten.
Before each subsequent dose, careful evaluation is performed to look for any symptoms. If symptoms occur, and the medical personnel judge that a reaction is happening, the feeding is stopped and medications are given as needed. Otherwise, the feeding continues until, typically, a meal sized portion is eaten.
Most food challenges that result in a reaction trigger skin or stomach symptoms. The symptoms are usually mild because the testing is done gradually with very small amounts of food at the start, and feeding is stopped at the onset of symptoms. Most often, antihistamines are given for these mild symptoms. If there are more severe symptoms, treatments can include epinephrine and/or other medications.
If there were no symptoms during an OFC, usually patients are discharged from the office within 1-2 hours of completing the feeding. In case of allergic symptoms, the patient is typically watched for at least 2-4 hours from the time symptoms go away or improve, with longer observation periods required for patients with more severe reactions.
The risks of OFC include an allergic reaction including anaphylaxis. To date, no death from a physician supervised OFC has been reported in the medical literature. There is no evidence that having an allergic reaction during an OFC makes future reactions worse or prolongs allergy in children.
The benefits of food challenges include the nutritional and social benefits of being able to expand the diet if the food is successfully eaten without symptoms. However, even if the food triggered a reaction, the benefit is knowing that the food is truly a problem and needs to be avoided to maintain health.