Food allergies can be frustrating, especially if you don’t know what is causing your symptoms. If you think you have a food allergy, you’re not alone — it's estimated that as many as 250 million people worldwide suffer from at least 1 food allergy. [1] In order to figure out what is actually causing your allergic reactions, you will need to keep a food diary. By writing down everything you eat and the symptoms you experience, you and your doctor will be able to determine exactly what food allergy you have.

Method 1
Method 1 of 4:

Writing Down Everything You Eat

  1. Make sure your food diary is small enough to carry around with you wherever you go, but large enough to write down all the information you’ll be tracking. You’ll want to have columns for the date, time, everything you eat, and any symptoms you experience.
    • You can also download an app to your phone or tablet by searching for ‘allergy diary.’ There are a number of free food allergy apps you can use, but some apps may cost a small fee to download. [2]
    • Record any time a symptom is worse or better.
  2. Keep track of meals, snacks, and even supplements, no matter how much or how little you eat. Write down all of the ingredients in each meal, including condiments. [3]
    • Be as specific as possible. Instead of writing down ‘Sandwich’, you would write ‘Wednesday, 12 p.m.: Ham sandwich on white bread with mayo, cheddar, and brown mustard.’
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  3. There can be hidden allergies in drinks, including juices and cocktails. Keep track of all of your beverages throughout the day and the portion you drink. [4]
    • Include the ingredients that go into your drink. For example, you might write down “Thursday, 10 p.m.: 5oz chocolate milk (2% milk and Hershey’s chocolate syrup).”
  4. As the day progresses, you will forget about things like the bagel you had in the breakroom or the bag of chips you grabbed on your way to class. By writing down each item as you eat it, you will be better able to keep track of the cause of your allergies. [5]
  5. Your allergy may be triggered when you eat a certain amount of food. Get in the habit of measuring the food that you eat to determine your portion sizes, and write those portions down. [6]
    • Use measuring cups and a food scale to keep track of your portions. You can estimate portion size when you’re dining out. This will get easier as you get more practice in measuring what you prepare at home.
    • You don't have to count every item you eat, but keep a close estimate. Instead of writing down "a handful of grapes," write down "about 12 grapes."
  6. As strange as it seems, some people are allergic to things when prepared one way and not another way. This is because they are actually allergic to the ingredients used to cook the food, rather than the food itself. Keep track of whether the food is fried in vegetable oil, sauteed in olive or coconut oil, or cooked with butter.
    • An example entry might read: "Monday, 6 p.m.: 1 cup angel hair pasta tossed with olive oil topped with 5 large shrimp sauteed in butter, with 1/2 cup steamed broccoli on the side."
  7. Some people have food sensitivities triggered by additives in processed food, like red or yellow dye. [7] Take a picture of the label, cut it out and paste it into the diary, or write all of the information down in your notebook.
  8. Try to stick to restaurants where the ingredients are listed on the menu. (This is more common as awareness around food allergies is growing.) If your restaurant doesn’t list ingredients, ask the server about what is included in the dish. [8]
    • If you do determine that you have a food allergy, you’ll need to get comfortable asking your server about the ingredients in menu offerings, so this is good practice.
  9. Being aware of common allergens can help you quickly pinpoint your food allergy. Common allergens include milk, eggs, peanuts and tree nuts, soy, wheat, fish, and shellfish. [9]
  10. 10
    Record medicines, vitamins, supplements, and snacks, as well. Anything that enters your stomach should be recorded in your diary. Take note of not only snacks and desserts, but also things like vitamins, supplements, and medicine.
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Method 2
Method 2 of 4:

Keeping Track of Symptoms

  1. You should include the time symptoms start, their intensity, and when they start to go away. Be as specific as possible about how you feel. Symptoms can begin just a few minutes after eating a food you’re allergic to, but it may take up to 2 hours for symptoms to appear. Record your symptoms before you eat each meal or snack, as well as 30-60 minutes after you eat. [10]
    • Assign a numerical value to the severity of your symptoms. For instance, you could rate your nausea on a scale of 1-5. [11]
    • An example entry might be: "Monday, 7 p.m.: Slightly itchy throat (2/5) and face was flushed."
  2. These symptoms may affect your skin, throat, respiratory system, or gastrointestinal system. If you know what to look for, you’ll be more likely to notice any symptoms, even if they are very mild. [12]
    • Some foods may cause irritation of the neck or face, including itching, swelling, hives, and flushing.
    • Gastrointestinal distress is a common effect of a food allergy. You might experience nausea and vomiting, bloating, gas, or diarrhea after eating certain foods.
    • Other symptoms of a food allergy might include fainting, difficulty breathing, low blood pressure, wheezing, headache, or pain in the ears.
  3. If you start experiencing symptoms after eating, ask anyone who shared your meal if they feel the same way. The symptoms of food poisoning, such as nausea or bloating, can resemble those of food allergies. [13]
  4. If you experience the same symptom multiple times, see if you can find a common ingredient in your food diary. Remember to look back a few hours in case the food causes a delayed reaction.
    • If you experience nausea and you see that it occurs whenever you eat bread or pasta, you may have Celiac disease, which is an allergy to gluten.
    • If you get hives whenever you eat peanut butter, you may have a peanut allergy.
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Method 3
Method 3 of 4:

Performing an Elimination Diet

  1. Using the patterns you've found, determine which foods are potentially causing your symptoms. Eliminate about 5 foods from your diet completely for about 2 weeks. [14]
  2. If your allergic symptoms subside, add in 1 food at a time every 3 days. This will give your body time to process each food, and you will be able to tell if that food is causing your symptoms. [15]
  3. If you notice your symptoms coming back, write down which food you added back into your diet for that period. If the reaction is uncomfortable or severe, remove it from your diet again right away. [16]
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Method 4
Method 4 of 4:

Getting Tested for Food Allergies

  1. An allergist is a doctor who specializes in the treatment of allergies, asthma, and the immune system. Your doctor will help you determine the exact cause of your symptoms and the best way to treat them. [17]
  2. A food diary is not intended to be a substitute for medical treatment. Instead, it should be a tool to help you and your doctor determine the cause of your discomfort. Armed with your food diary, your doctor will be able to get to the bottom of your allergies more quickly.
  3. A skin prick test involves marking a grid on the skin, then lightly scratching the skin with needles containing various allergens. If the skin reacts, the doctor will know you are allergic to that substance. A blood allergy test looks for antibodies in the blood which trigger the symptoms of food allergies. [18]
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      Warnings

      • Do not use a food diary to diagnose food allergies if you have experienced anaphylaxis, which is a severe, life-threatening allergic reaction.
      • The food diary is not intended to be a substitute for professional medical advice.
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