If you’re experiencing ongoing symptoms in reaction to food, like chronic GI problems, hives, or rashes, you may have come across the term “elimination diet” in your search for answers. As a certified allergist, I often use elimination diets as a tool to help diagnose food allergy and find food intolerances. Here, I’ll explain how elimination diets work, how they should be integrated with food allergy testing, and the process I use to advise an efficient elimination diet plan with my patients.
What is an elimination diet?
A food elimination diet is used in conjunction with IgE blood or skin prick allergy tests, along with a health history to diagnose food allergy. Doing an elimination diet can also help identify foods that you’re otherwise intolerant of or sensitive to.
An elimination diet involves removing a specific food (or group of foods) from your diet for a set period of time, then reintroducing it. Elimination and reintroduction is a step-by-step methodology — something that needs to be done with precision and care, especially to avoid nutritional deficiencies during the elimination phase if many foods are being removed from the diet. Elimination diets can take weeks, and require hypervigilance when reading food labels, avoiding specific foods, and keeping a meticulous food diary.
Because the goal is to identify foods that are causing symptoms, elimination diets should always be done under the guidance and supervision of a certified allergist, dietitian, or another food-allergy specialized healthcare provider to mitigate severe reactions.
The concept of an elimination diet goes back to the 1940’s, when Albert Rowe published ‘Elimination Diets and the Patient’s Allergies’ which contains concepts that are still used in practice today.
How an elimination diet works
Specific protocols may vary from patient to patient and practice to practice. In my practice, I usually have patients eliminate individual foods for a period of eight days. (Some protocols go beyond this — for up to weeks at a time.) During the elimination period, we observe whether removing the food is helping resolve the symptoms that brought the patient to me in the first place.
Single food vs. multiple food elimination
Most often, foods are removed from the diet one at a time. But occasionally in people who are experiencing allergy symptoms like total body hives that require steroid treatment, many foods are eliminated all at once. This approach may help get symptoms under control, and can make the process of figuring out the problem food(s) a lot easier, since it’s like starting from scratch.
Reintroduction through oral food challenges
After the elimination period, the food/foods that have been removed are reintroduced through an oral food challenge. Essentially, a food challenge is the process of eating the foods you’ve eliminated and seeing how your body reacts. I most often use an at-home challenge for patients who experience less severe food allergy symptoms like digestive discomfort, mild hives, or rashes. People who have experienced anaphylaxis, a severe allergic reaction that sends the body into shock and requires immediate medical treatment, shouldn’t reintroduce foods on their own at home and need to do a food challenge under a medical professional’s supervision.
Elimination diets as a form of treatment
An elimination diet may also be used as a form of treatment. For instance, if you confirm through an IgE blood test, skin prick test, and/or an oral challenge that you’re allergic to wheat, a diet that eliminates wheat may be part of your treatment plan. Similarly, people with certain conditions, such as eosinophilic esophagitis (EOE), might be prescribed an elimination diet that removes some of the most common food allergens as part of their treatment, which might be reintroduced as part of a challenge in the future, after medical treatment.
Why do an elimination diet?
Why do we recommend medically-supervised elimination diets when food allergy testing is available? Because food allergy and sensitivity testing is both art and science. In my opinion, an elimination diet and oral food challenge is the only way to truly confirm a certain food is the problem (unless the patient has an intense allergic reaction any time the item is consumed, for example, they have anaphylactic reactions to peanuts).
Food allergy tests are reliable, and we’ve certainly come a long way in testing — even at-home testing. IgE blood tests are the main method of food allergy testing, along with IgE skin prick testing. These tests measure the presence of immunoglobulin E antibodies, which indicate an immune system reaction to a given substance. These tests are very helpful and can tell us a lot about the foods a person may or may not be allergic to, which you can read about in my complete guide to food allergy testing. But they’re not perfect!
Sometimes IgE tests will come up positive for a food the patient has never had a reaction to. This can happen because they’ve built up a tolerance to the food, or because of what’s known as a cross-reaction. For example, shrimp and dust mites have a protein in common that some people are allergic to. If a person is allergic to dust mites, they might test positive for a shrimp allergy, even though they’ve never had a reaction to eating shrimp. Other common cross reactions include cashews and pistachios, and walnuts and pecans.
The importance of combining diagnosis strategies
The combination usually includes at least a detailed medical history, laboratory testing, a guided elimination diet, and an oral food challenge.
Also, before I do food allergy testing, I always tell my patients not to be surprised if it comes back negative. A negative result doesn’t mean their symptoms aren’t valid. It might mean that they have a food intolerance or hypersensitivity that can’t be detected through blood or skin prick testing, or that their particular allergy wasn’t tested for. They might also be allergic to something other than food.
An elimination diet and oral food challenge can help fill any gaps left by the food allergy test results, and can also help prove that the blood or skin prick test results are correct. In fact, sometimes you can figure out what the problem food is through elimination and reintroduction alone.
Still, I usually use elimination diets and food allergy testing in combination, as both the test and diet results can guide which foods should be eliminated and challenged next.
How to do an elimination diet
Here’s the process I use for food elimination diets and challenges with my patients. And yes, I might sound like a broken record at this point, but whether you’re doing just an elimination diet or combining it with food allergy testing, you’ll want to get the guidance and supervision of a certified allergist, food-allergy specialized dietitian, or other qualified provider before getting started with eliminating and challenging foods.
For me, the first step is getting the patient involved in the process, and getting them on board with working together to find answers through an elimination diet. Keeping a food diary, eliminating foods, and then challenging them aren’t easy tasks. Committing to the process is key.
Step 1: Create a detailed two-week food diary
After you've fully committed to doing an elimination diet, the next step is to keep a thorough and detailed food diary for two weeks. When I say detailed, I mean really detailed. So you’re not just going to write “salad” for lunch. You’ll write, “baby spinach, cherry tomatoes, red, pepper, feta cheese, chicken breast, olive oil, vinegar.” You’ll need to start reading labels and including anything that might be noteworthy in your food diary. Do the crackers you just ate contain eggs, dairy, and soy, on top of wheat? Are there garlic and onions in the flavorings of foods that make you ill? You’ll have to help me help you by playing detective in your own pantry and refrigerator.
In the diary, I also ask my patients to record how they’re feeling a few hours after each meal or snack, noting any symptoms like bloating, digestive discomfort, rashes, or hives. These can be important clues when we’re deciding on foods to eliminate and challenge later on.
The food diary is particularly useful because people often think, for example, that they don’t eat a lot of dairy, so dairy probably isn’t the thing that’s causing their symptoms. But then through their food diary, they discover that they really do eat a lot of dairy because they’re having yogurt with breakfast, cheese at lunch, and ice cream for dessert. Milk, for example, is found in food where you might not expect it like baked goods, crackers, and candy.
Interestingly, research has shown over and over again that people aren’t great at remembering what and how much they ate. I’ve found the same to be true in the context of food allergy. People often don’t realize just how much of various potential allergens they’re eating, and the food diary can be really revealing for that reason.
In terms of timing, if you’re doing IgE blood testing, the food diary can be completed while waiting for the test results.
Step 2: Analyze the food diary to look for patterns
Once the food diary is complete, there are two main questions I ask:
- Which foods are you eating most frequently in general?
- Which common allergens appear frequently in your diet?
I usually comb through the food diary with my patient and list out the 10 most common foods in their diet. From there, we’ll cross-reference those with the most common food allergens:
- Tree nuts (ex. walnuts, almonds, cashews)
- Shellfish (ex. crab, shrimp, lobster)
I take the food allergy test results into account, then come up with a list of foods to eliminate and challenge in a systematic way. We start with the foods that are most likely, in my opinion, to be the problem, and work our way down to the foods that are less likely.
It’s great to note down your own observations as you create your food diary about which foods you’re eating frequently and which ones seem to be causing symptoms. But your allergist or dietitian is trained to notice things in food diaries that the average person might not, so making this stage a collaborative process is key.
For instance, some people may not know all the foods that contain dairy, wheat, and soy, since these ingredients are often present in foods you might not expect. But a person trained in elimination diets and who is skilled at food allergy diagnosis will know exactly what to look for and will be knowledgeable about which foods contain which ingredients.
Step 3: Systematically eliminate potential problem foods
This part is simple. Starting at the top of your list, you take one food out of your diet for eight days. I usually have my patients do this from Saturday to Saturday to keep things easy. People typically find it easier to start on a day when they’re not working, and it helps provide structure to have a set schedule. Being on any type of diet can be challenging, and structure can help with sticking to it.
In some cases, there are food substitutions that my patients find helpful:
Usually, foods are eliminated and then reintroduced (see step 4) one at a time. The main exception is with foods like garlic, onion, and tomato, because they’re often eaten together in lots of different types of cuisine. So sometimes it’s easier to just eliminate all three at once, then reintroduce each one separately.
If an issue with dairy is suspected, I will ask the patient to use lactase digestive enzymes before eliminating dairy, to see if the symptoms improve using this over-the-counter enzyme.
And as I mentioned earlier, anyone dealing with extreme food allergy symptoms would likely need a more restrictive elimination diet that involves eliminating many foods at once in order to help relieve symptoms. But this doesn’t apply to most people. Still, if you’re eliminating several foods at once, trying to keep a balance of protein, fat, carbs, and vegetables at each meal can help ensure you're meeting your nutritional needs.
Step 4: Reintroduce potential problem foods one by one
On the Sunday after your eight day elimination period, you’ll reintroduce the food you eliminated, a process known as a challenge. I do this challenge over the weekend, in case the symptoms from reintroducing a food are unpleasant and interfere with work days.
In order to do a food challenge, you’ll want to eat that food twice in one day, usually in close succession. So if my patient eliminated milk in the previous step, I'll have them drink a glass of milk Sunday morning, then wait an hour. If they experience symptoms, we stop there, noting down exactly what they’re experiencing. We now know that milk is one of their problem foods. From there, we may still eliminate and challenge a few other foods, depending on their specific situation.
If they’re not having any symptoms with that first glass of milk, then they’ll drink another glass of milk. If they still feel good after monitoring their symptoms for several hours, we can say pretty conclusively that milk isn’t a problem food, and we move on to the next food to eliminate.
Once we’ve identified the problem food(s) through this process, those foods are removed from the person’s diet. Depending on whether the problem food is a true allergen or an intolerance, it may be possible to reintroduce it again after a few months or years as part of another food challenge to see if the reaction has changed.
For some people, oral immunotherapy (OIT) may also be an option. OIT is a newer form of allergen management typically only used for severe peanut allergies — for now, at least. OIT gradually re-introduces true food allergens in very small amounts until they can be tolerated in increasing doses. Because some severe food allergies can cause anaphylaxis, OIT must be done under the supervision of a certified allergist.
What you need to know about doing an elimination diet
It’s worth noting that elimination diets can be really challenging. Writing out a detailed food diary and eliminating foods from your diet takes work and discipline. I think the most important thing to know before you do an elimination diet is that you have to be fastidious with it. If you’re eliminating eggs, you truly can’t have anything with egg in it for a full eight days before you introduce them. Even a small amount, even in baked products, can skew the results.
For most people, this means they need to prepare their own foods during the elimination diet process, as most restaurants can’t guarantee that they won’t contaminate food with potential allergens.
But in the end, the process is worth the effort. Combined with smart testing, an elimination diet truly is the gold standard in diagnosing food allergies and food intolerances.