Approximately 12 million Americans have a food allergy, including 4 million children.
Eight foods account for 90 percent of all reactions in the United States: cow’s milk, hen’s eggs, peanuts, tree nuts, wheat, soy, fish and shellfish. Other food allergies range from avocados to yams.
Most food allergy symptoms are mild, but in the United States there are approximately 30,000 episodes of food-induced life-threatening anaphylaxis, associated with 100 to 200 deaths annually. The only way to prevent an allergic reaction is to avoid foods you are allergic to, so an accurate diagnosis is essential.
Studies show however, that more than half of presumed food allergies are not actually allergies.
It’s an important distinction. “You don’t want to avoid food that you are not allergic to,” says Jay Portnoy, MD, “but you do want to avoid foods that you are allergic to. Board-certified allergists can be helpful in determining this because they have special training and experience in interpreting the results.”
Guidelines for the Diagnosis and Management of Food Allergy in the U.S. (National Institutes for Allergy and Infectious Diseases, December 2010) provide in-depth information on what works and doesn’t work when it comes to food allergy.
The first thing a physician looks at when diagnosing food allergy is your history of symptoms. Common symptoms include a tingling sensation in the mouth, swelling of the tongue and throat, or difficulty breathing; skin problems such as generalized hives or itching and flushing; stomach discomfort such as abdominal cramps; diarrhea, or vomiting; or a drop in blood pressure, dizziness or loss of consciousness. They usually appear within minutes of eating the food, though they can sometimes appear hours later.
If you think you might have a food allergy, keep a written diary with the following information:
- What exactly did you eat and how much?
- Where and how was the food processed? Was it at home? A restaurant?
- How was the food prepared: raw? boiled? roasted?
- Were you doing anything else during or just after your meal, like exercising?
- What kind of symptoms did you notice?
- How long after consuming a food or liquid did you notice symptoms?
- How long did the symptoms last and how severe were they?
- Did you do anything to help ease the symptoms (such as take prescription or over-the-counter medications)?
Show your diary to your healthcare provider. Quite often, the food allergy will be obvious but follow-up testing is important to confirm the diagnosis.
Food Allergy Testing-
The food allergy tests performed most often by allergists are skin prick tests. A diluted extract of the food is placed on the patient’s skin, then the skin is scratched with a needle. If you develop a raised skin reaction (called a wheal) at the place of the needle prick, that indicates possible allergy. If there is no reaction, you are unlikely to be allergic to the food.
Skin prick tests are quite accurate for foods with stable proteins, including peanut, milk, egg, tree nuts, fish and shellfish – some of the most common food allergens in the United States. They are less reliable for fruits and vegetables, which have proteins that break down quickly.
Blood tests that look for IgE antibodies (particles in the blood that indicate allergy) are also useful for identifying food allergies. These are particularly helpful for people whose allergy history puts them at high risk of serious reaction to a skin prick test; whose skin problems make skin-prick uncomfortable or dangerous; or who take certain medications that interfere with skin prick test results.
No test is perfect, however. A positive skin or blood test response does not necessarily mean that you would have an allergic reaction from eating the food. “Just because you have a positive test to a food doesn’t mean you are allergic to it,” explains Dr. Portnoy. “Personally, I’m still seeing a lot of patients who have been told not to eat foods because of positive test results, when in fact they have never had a problem with the food.”
Food allergy guidelines say the diagnostic tests to evaluate food allergy should be based on the patient’s medical history and not be comprised of general large panels of food allergens. Patients who test allergic to numerous foods might choose to eat very restrictive diets, which can be unhealthy and difficult to follow. That’s why seeing an allergist trained to put all the evident together for a diagnosis is important.
NIH Food Allergy Guidelines recommend your healthcare provider may use an oral food challenge test to diagnose food allergy. Because an oral food challenge test always carries a risk, it must be performed by a healthcare provider trained in how to conduct this test and at a medical facility that has appropriate medicines and devices to treat potentially severe allergic reactions.
If you or your child has been diagnosed with a food allergy, talk with your healthcare provider about how to avoid reactions. Ask for a written anaphylaxis action plan. For children with food allergies, give a copy of the action plan to the school and all caregivers.
Early recognition and treatment of symptoms is critical.
Most often, you will need to completely avoid eating the food you are allergic to. If you have a life-threatening food allergy, your healthcare provider will prescribe auto-injectable epinephrine to use in anaphylactic emergency situations. Be sure you know how to use it and carry it with you always. Make sure school, family, friends and other caregivers are also trained on how and when to use epinephrine. Consider wearing a medical alert bracelet that lists foods you are allergic to and has instructions to give you epinephrine if you are unable to do so yourself.
Many children will outgrow their food allergies over time, particularly if they are allergic to milk, egg or wheat. It is less common to outgrow an allergy to peanuts or tree nuts, although it is still possible. So it is important to maintain a close relationship with your allergist who can help you to determine whether the food allergy is still problematic.