This test can cause a serious allergic reaction, and should only be conducted by an allergist within a medical facility. A food challenge test is the last test that will be conducted, if the skin test and blood test are unable to give a proper diagnosis. For a food challenge, the allergist will give you a dose of the suspected food. It will start small and if no symptoms are shown, then the dose will increase. Once you show signs of a reaction, the test will stop. Severe reactions are not common and proper medications will be given as necessary.
A food challenge allergy test, or oral food challenge, is administered in your allergist's office under direct supervision. The test will begin by your allergist feeding you small doses of the food that is in question. If there is no reaction, then the doses will gradually increase until you reach a full serving of food. If there is a reaction in the middle of the test, then the test will end. Typically, there are no major reactions to the allergy tests, but you are under strict supervision just in case.
In a double-blind, placebo-controlled food challenge, neither the allergist nor the patient know which food item will be a placebo or the actual allergen. This allows for the testing to be completely impartial, and does not allow for nerves or the allergist's preconceptions to get in the way of testing. In a single-blind food challenge, the allergist knows which food is the placebo but the patient does not. The most common type of food allergy test is an open-food challenge. An open-food challenge is where the allergist and the patient both know that the allergen is being given. This is typically done during one office visit.
A food allergy test is a very length process. A few weeks before the food challenge allergy test, you will want to make arrangements for the other members of your family. For example, if you are taking one child to be tested, you will need to make arrangements for the other children. About five days before the test, you will want to end use of any antihistamines, as specified by your allergist. The day before the test, you will need to confirm your plans are still standing, and that you have packed all of the items that your allergist recommended on bringing. Some items that your allergist may recommend bringing are things for your child to do while they wait, change of clothes for your child in case they get sick, change of clothes for you, the subject food, safe food, and two epinephrine injections.
If you or your child also has asthma, then you will want to not take the dose of albuterol the day of the test. On the day of the test, you need to be completely healthy. If you have an asthma flare up, then you will need to call the clinic and discuss what steps to take. If you are having any other problems, you will need to call the office and reschedule your appointment. You will also want to ask your allergist if you should eat anything on the morning of the test. After the test is administered, your allergist will request that you stay in the office for up to three hours if there is no allergic reaction. During these three hours, the allergist will be watching for any signs or symptoms to appear. You may have to wait for four hours if there is an allergic reaction.
During the test, no other food or drinks are given. If the test is being done on children, then the allergist will not trick or bribe the child into eating the allergen. In some cases, they may mix the allergen with another food in order for it to be tasty, but with full consent of the child and family. The test is done under a high level of supervision and in a safe environment. The nurse and physician will be watching for symptoms to appear and will have the necessary medications on hand in case of a reaction.
During a food challenge, there is the risk of an anaphylaxis reaction. There is no proof that partaking in the food challenge allergy test makes future reactions worse or prolongs allergies. If there are any minor reactions to the food, then the allergist will give you something to relieve the symptoms. Once you have passed the food challenge allergy test, then it is highly uncommon that you will have an allergic reaction later in the day.
The food challenge allergy test can have one of two outcomes. You can make it through the whole test with no allergic reaction, or on the other hand, you may only make it a few doses in and have a reaction. If there is no allergic reaction, then you know that you can add that item back into your diet. If you have a food that triggers a reaction, then you will need to eliminate that food from your diet and come up with an allergy action plan with your allergist.
A food challenge allergy test can be done in children and adults under strict supervision of an allergist. The foods most commonly tested are: dairy, eggs, grains, nuts, soy, and fish. The food challenge can be completed one of three ways- through a double-blind test, a single-blind test, or an open test. The most common way is through an open test. The test may take up to six hours in the allergist's office. Extreme reactions to the test are rare. The outcome of the test is either a pass or a fail. If you pass the test, then you are able to introduce the food back into your diet. If you fail, then you will need to avoid the food and speak with your allergist about developing an allergy action plan.
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