Food allergies are on the rise worldwide, as is research into possible causes and cures. But even though doctors are seeing more patients with food-related symptoms, correctly diagnosing food allergies remains tricky.
Most of us eat multiple ingredients with every bite of food we take. So stomach cramps from eating spaghetti and meatballs could be the result of tomato allergy if you used tomato sauce, egg allergy or gluten intolerance from the pasta . . . even food poisoning. Not all reactions to food are allergic reactions. In addition, food allergy symptoms can start two minutes or two hours after you eat a certain food – making it difficult to pinpoint what caused the reaction.
Food allergy tests are important diagnostic tools but aren’t enough to close the case. If you test negative to a food allergen, that diagnosis sticks. But positive results are a different matter. According to Robert Wood, MD, in Food Allergies for Dummies®, “Up to 60 percent of all positive food skin tests turn out to be incorrect (false positive).” Why the confusion? Two possible reasons are
- Your immune system has a small amount of IgE antibodies – your defenders against invading allergens – to a food but not enough to cause an allergic reaction.
- You are allergic to a related food or environmental allergen (like pollen). This situation is called cross reactivity.
Blood tests can be thrown off by the same scenarios. Before you take platefuls of food off your menu – and miss out on meals packed with nutrients and health benefits – use a food diary to help confirm or rule out a food allergy.
Just as food journals have helped dieters around the world cut calories and fat, a food diary can help you focus in on possible food allergies. Keep a small notebook handy in your purse, briefcase or backpack to make quick journal entries at each meal. Items to include:
- What you eat and drink
- Symptoms you think may be the result of a food allergy
- What you were doing at the time your symptoms started
Look Out Stomach, Here It Comes
To root out the cause of food allergies, you’ll need to transform yourself from casual diner to food detective. The suspect could be your breakfast cereal, steak dinner or even that pack of breath mints. If it goes in your mouth, it should go in your food diary! Include all the ingredients, how your food is cooked (such as grilled vs. fried in peanut oil) and the amount you consume.
Hidden ingredients like flavorings, dyes and preservatives can cause allergic reactions in some people. When food labels start to look like chemistry lists, it may be easier to just cut out and save the labels. Borrow a pocket folder from your child’s school supply stash to keep labels handy and in one spot.
Most restaurants are becoming quite food allergy aware these days. When dining out, look for places that offer ingredient lists and ask the restaurant manager for labels from packaged foods used in any of the dishes you’ve been served. It may be easier to dine-in or limit your diet to foods with few ingredients until you solve your food allergy mystery. And if you find that you haven’t had symptoms since you stopped eating at your favorite Italian restaurant . . . that tells you something!
If you’re eating with family or friends when symptoms strike, ask around – did anyone else eating the same food get sick? Think back to the time before you started having food issues. Had you been able to eat a suspect food without problems? How often did you eat it? Jot down notes to share with your doctor. It will help with your diagnosis.
While you’re keeping track of what goes in your mouth, add suspected food allergy symptoms that come up. Allergic reactions can range from annoying to life-threatening – and move quickly from one to the other. So take note of any possible symptoms, including
- Tingling or itching in and around the mouth
- Swelling of the tongue and throat
- Flushing of the face or neck
- Eczema (if symptoms get worse after eating)
- Hives and swelling
- Abdominal cramps
- Difficulty breathing
- Drop in blood pressure (feeling faint or weak)
- Loss of consciousness
Include when symptoms started and when you felt them go away, whether you were drinking alcohol when the symptoms occurred (which can increase your body’s absorption of a food allergen), whether you took any medications to treat symptoms and any other medications you were taking at the time. Get immediate medical help for severe symptoms.
Time Out on the Treadmill
Exercise can also be a factor in food allergies. AANMA President Nancy Sander recently sat next to a woman on a plane who had exercise-induced anaphylaxis to tomatoes – if she exercised too soon after eating anything with tomatoes, she experienced symptoms of anaphylaxis! If you think you’re having food allergy symptoms, include a note about what you were doing right before or during the time you had the reaction (like taking a walk outside or sweeping the floors).
Over time (it could be days, weeks or longer), you and your doctor may start to see patterns between what you’re eating and allergy symptoms. Look for consistency: Do all milk products give you stomach cramps or do you feel ill only after drinking a glass of milk?
More than 90 percent of allergic reactions to food in the U.S. are due to 8 foods or food groups:
- Tree nuts
Manufacturers are now required to label allergens in these terms on food labels. You could also fall into the other 10 percent of cases ranging from avocados to yams. Your food diary can help you identify even the most unlikely of food allergy suspects.
From Diarrhea to Diagnosis
Food diaries, allergy tests, medical history . . . you and your medical care team have a range of clues to detect possible food allergies. Where do you start? In Food Allergies for Dummies, Dr. Wood suggests a visit to your general practitioner (GP) – family physician, internist or pediatrician – first. Your GP will perform a physical exam and take your medical history, which is the most important step in ruling out other causes of your symptoms. If food allergies are still a possibility, your GP can refer you to a board-certified allergist experienced in diagnosing and treating food allergies. If you have asthma or allergies, you are probably already working with an allergist, so check with your allergy team on how to proceed. In either case, your food diary will help you and your medical care team identify likely food allergy culprits and start you down the road to better health.
First published: Allergy & Asthma Today, Fall 2007
Updated: February 2009