Also called: Elimination and Challenge Diet
An elimination diet is used to identify and remove foods and ingredients that provoke allergic reactions in a patient. During this process, patients eliminate all suspected foods or ingredients from their diets for a period of time. Patients who eventually find themselves symptom-free then gradually reintroduce suspected foods back into their diet, one by one. When a reintroduced food sparks a reaction, an allergy diagnosis is usually made. An elimination diet can also be used to detect some food sensitivities or intolerances.
A food challenge test is a variation on the elimination diet. This test takes place in a controlled environment in a single session. During the test, a physician exposes the patient to suspected foods or ingredients in hopes of actually provoking an allergic reaction.
Elimination diets and food challenge tests can accurately reveal the nature of a patient’s food allergy. However, the tests can be time-consuming, and establishing a connection between an allergen and a reaction can be difficult. In addition, they may be too dangerous for those whose food allergies provoke anaphylactic shock, a life-threatening, whole-body allergic reaction. It is very important that an elimination diet be performed only under a physician’s supervision.
An elimination diet usually lasts for a period of weeks. Over this period it is important that a patient conscientiously follow the diet without cheating. Straying from the diet even a little can ruin the diagnostic capability of the test.
About elimination diets
An elimination diet is used to pinpoint foods or ingredients that are responsible for adverse reactions, such as allergies, sensitivities or intolerances.
A food allergy is an adverse and potentially fatal response by a person’s immune system to a food or food component. After a susceptible person ingests a problem food, the immune system releases histamines and other hormones that trigger symptoms that can range from mild to life-threatening. About 90 percent of all food allergies have been traced to the following foods:
- Cow’s milk
- Tree nuts
Although the condition is not confirmed by the general medical community, reactions may occur when an individual consumes or comes into contact with one of many types of substances classified as a food additive—an ingredient that is not considered a part of its basic raw ingredients. Only sulfite additives have been proven to provoke an allergic reaction in some rare cases. Other additives that may trigger sensitivities include:
- Flavor enhancers
- Added nutrients, such as vitamins and minerals
- Stabilizers, emulsifiers and thickeners
- Food colorings
Food intolerance involves the inability of the body to digest a substance, leading to symptoms of discomfort (e.g., stomach cramping), but usually poses little danger. Unlike a more serious food allergy, intolerance does not involve an immune system reaction. Food intolerance often allows the individual to eat small portions of a problem food without experiencing symptoms. With a food allergy, even a very small portion of a food allergen can cause an allergic reaction.
During the elimination diet, patients remove all suspected food allergens from their diet. Elimination diets are typically used for several weeks. A shorter testing period may be used in some cases, such as with young children. If symptoms disappear during this time, an allergy or intolerance to one of the excluded foods or ingredients is strongly suspected. The foods that are most frequently consumed by the patient are often the foods that cause allergic reactions.
To help confirm this diagnosis, the patient slowly resumes eating the restricted foods one at a time at intervals of three to seven days. The patient watches for and records any signs of an allergic reaction. If a reaction occurs, a food allergy diagnosis becomes more likely.
Elimination diets are not practical for patients who have allergic food reactions that result in anaphylactic shock. This condition is a life-threatening, whole-body allergic reaction that demands immediate emergency medical attention. This danger makes elimination diets too risky for individuals with a history of anaphylactic shock.
Finally, psychological and physical factors can affect test results. Patients who expect to have reactions to a food can sometimes induce symptoms, even if an allergy is not actually responsible.
It is important that a patient conscientiously follow the elimination diet without cheating. Even a small amount of cheating can ruin the diagnostic capability of the test.
An elimination diet should be performed only under the supervision of a physician. In addition to the risk for anaphylactic reaction, people who attempt an elimination diet on their own also risk nutritional deficiencies. The random removal of foods from a person’s diet can cause a lack of nutrients, leading to a number of possible health problems. Patients should not make significant changes in their diet without first discussing it with their physician. Individuals undergoing an elimination diet may benefit from consulting with a dietician. These trained professionals can help people plan a well-balanced diet while eliminating potential allergens.
Before, during and after elimination diets
Before diagnosing a food allergy, a physician will take a medical history and perform a physical examination of the patient. The medical history also can provide crucial clues to the nature of a food allergy or intolerance. The physician is likely to ask about several aspects of the allergy, including the nature of the reactions—when they occur, how quickly they come on, and whether they are always associated with the same foods.
Sometimes, it is possible to make a diagnosis based solely on the patient history. In such instances, a patient may be asked to keep a diary of each meal, including foods consumed and any reaction to them.
An elimination diet is the next likely step. The physician asks the patient not to consume certain foods or ingredients for a few weeks, while suggesting alternative sources of any lost nutrients. For example, patients who eliminate eggs receive suggestions for other sources of protein. It is also best if patients can eliminate all other possible sources of an allergy, such as medications, vitamin pills and exposure to any other triggers known to cause allergies in the individual being tested.
During the testing, the patient must be very careful not to consume any amount of food that contains the restricted allergen. The patient will have to carefully read all food labels and inquire about food preparation methods when dining out.
The elimination diet often involves two stages. The first stage excludes the most common food allergens (e.g., milk, eggs, wheat, soy, corn). The second stage is eliminating many foods except those that, as directed by the physician, are least likely to create an allergic reaction. The foods permitted in this stage will vary from person to person.
In rare instances, a physician may recommend fasting as a method of detecting food allergies. Although this is an extremely effective method for identifying food allergens, it is usually reserved for people who are suspected of having multiple food allergies.
If the patient’s symptoms disappear during the period when foods are restricted, a food allergy or intolerance diagnosis is likely. If a food allergy is suspected, foods usually are reintroduced, one-by-one, at intervals of three to seven days. Suspected foods are typically eliminated for about three weeks before being reintroduced in the following sequence:
- Fruits and vegetables
- Poultry, seafood, eggs, red meat and dairy products
- Cocoa, sugars, nuts and grains
Each time a food is reintroduced, the patient keeps a record of every food consumed, and any symptoms that might reappear.
If symptoms do return, it adds further weight to suspicions that a food allergy is present. The food is eliminated from the patient’s diet one more time. If symptoms disappear once again, the allergy diagnosis is confirmed.
Some physicians may also want to confirm a diagnosis by performing a traditional allergy test, such as:
- Allergy skin tests. A small amount of an allergen is introduced to the patient’s skin to determine if the person is allergic to that allergen.
- Blood tests. A sample of the patient’s blood is tested for substances that indicate an allergic reaction has occurred to a specific allergen. These tests can sometimes detect substances that indicate food intolerance.
Factors that may impact results
Though elimination diets are often an effective tool for diagnosing food allergies and intolerances, they are not foolproof. Some foods have to be tested several times before a cause-and-effect relationship is established. Factors that can skew the results of an elimination diet include:
- Some people do not react every time they consume a certain food, and others react only after consuming large amounts of the food.
- Some patients appear to react to one food, but are actually suffering a delayed reaction to something eaten much earlier.
- Viral infections and other illnesses can lower a patient’s tolerance to a specific food allergen, falsely indicating a higher level of sensitivity than is normally present.
- Some patients can tolerate a little bit of a food, but react after consuming additional amounts of the food.
- The way a food is prepared and cooked can change its chemistry.
- A process called cross-reactivity can result in a person having an allergic reaction to certain foods or ingredients that contain similar proteins to another allergen. Foods that come from related families may cause similar allergic reactions, such as potatoes and tomatoes. In addition, when pollen counts are high, people with certain pollen allergies may experience a cross-reaction when they eat certain fruits with proteins similar to the pollen. This is referred to as oral allergy syndrome. The food reaction is therefore secondary and not a true food allergy.
- Many common food allergens are “hidden ingredients” in a variety of foods. To ensure a successful elimination diet, patients have to carefully read the labels on all foods eaten during the period when foods are restricted.
Potential risks with elimination diets
Anaphylactic shock is by far the greatest potential risk associated with an elimination diet. It is a rare, severe allergic reaction that affects the entire body and often begins immediately after an individual has been exposed to a particular allergen. This kind of reaction can be fatal and requires immediate medical treatment.
Occasionally, a patient who consumes a food allergen suffers an anaphylactic reaction. This can also happen during the reintroduction phase of an elimination diet. Without prompt emergency treatment, anaphylactic shock may interfere with a person’s ability to breathe. An emergency dose of epinephrine (adrenaline) is necessary to reverse these symptoms and potentially to save the patient’s life. For this reason, elimination diets should never be tried except under the strict monitoring of a physician.
Patients who begin an elimination diet are at risk of losing key nutrients. A dietician can help patients choose nonallergenic alternatives that replace nutrients lost as a result of excluding certain foods.
Treatments that may follow elimination diets
The only form of treatment for food allergies is the complete removal of problem foods from the diet. There are currently no drugs available that can prevent a food allergy from taking place. Food allergies can be deadly if avoidance is not practiced diligently.
A person can successfully remove troublesome foods from their diet by paying close attention to the ingredients in the foods they eat. Successfully controlling a food allergy requires a person to check the ingredient labels on foods at the grocery store and ask about ingredients and preparation techniques at restaurants.
If a reaction to a food allergy does accidentally occur, treatment is focused on relieving symptoms. There are a variety of medications that may be recommended depending on the severity of the reaction:
- Antihistamines. Medications that provide relief for more common allergy reactions such as hives, sneezing, runny nose and gastrointestinal symptoms.
- Bronchodilators. Medications that open the airways of the lungs, relieving symptoms such as shortness of breath or wheezing.
- Epinephrine injection. Used for the most severe allergic reactions involving life-threatening anaphylactic shock. Most physicians recommend that individuals who are susceptible to severe reactions carry an injection of epinephrine with them at all times and understand how to self-administer the drug.
- Corticosteroids. Medications that reduce inflammation. These medications are most commonly used to treat severe allergic conditions.
Alternatives and variations to elimination diets
A food challenge test is a variation on the elimination diet that also helps a physician to diagnose food allergies in a patient. During this test, a suspect allergen is deliberately introduced to the patient in a controlled environment. The patient consumes the food in pill form or disguised in a meal, and then is monitored for a reaction.
To further boost the odds of an accurate diagnosis during a food challenge test, a double-blind study is often conducted. In this approach, the food being tested is disguised to look the same as a placebo (an inert substance). Neither the patient nor the tester knows when the suspected allergen has been introduced. A third party monitor keeps track of whether the actual food or a placebo has been administered.
Food challenge tests are not routinely performed, and should only be conducted under the close supervision of a licensed medical professional. In rare cases, these tests can provoke anaphylactic shock, a life–threatening whole-body allergic reaction.
In recent years, alternative allergy tests have become increasingly popular—and controversial—methods used to “diagnose” allergies. Most healthcare experts are highly skeptical of these methods, saying there is little proof of their accuracy. Two alternative tests are used to diagnose food allergies:
- Cytotoxic testing. A blood test that supposedly identifies food or inhalant allergies. However, a number of clinic trials have found these tests completely ineffective at diagnosing allergies, according to the American Academy of Allergy, Asthma and Immunology (AAAAI). Such testing is therefore not recommended.
- Sublingual provocation and neutralization therapy. A combination therapy that supposedly identifies the allergen triggering allergy symptoms and then increases the patient’s tolerance of that allergen. It is unproven and not recommended by the AAAAI. The practitioner takes neutralizing substances—such as extracts of allergens, chemicals and foods—and injects them into the body or places them as drops under the tongue. Dosages are increased until the patient has a reaction. Once a reaction occurs, an allergy is diagnosed, regardless of whether or not an immune system response is involved. Additional doses of the allergen are then administered to “neutralize” the reaction.
Questions for your doctor on elimination diets
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about elimination diets:
- Why are you recommending that I participate in an elimination diet?
- How long will I have to adhere to this diet?
- Can I trust the results of this type of test?
- What risks do I face by participating in this test?
- Can I perform this type of test on my own?
- Can I eat small amounts of the restricted foods or will this ruin the accuracy of the test?
- What is the best way to make up for lost nutrients during the testing period?
- How can I identify restricted allergens in food products? What terms should I look for on food labels?
- Can I eat out during the testing period?
- Now that we have identified the problem food, what is the next step?