Food Allergy

Food Allergy

Milk, egg, sesame, peanuts, nuts and more

Around 5% of the population suffers from food allergies. Food allergy manifests with a recognized pattern typical of a reaction mediated by the immune system. Not all side effects to food are due to allergy.

For example, some people have low levels of lactase in their intestines (lactase is the substance that breaks down lactose, the natural sugar in milk). These people will have side effects (abdominal pain, "gasses" and/or diarrhea) after eating a certain amount of dairy products. However, they can tolerate small amounts. This is NOT an allergy. The side effects of lactose intolerance produce an unpleasant feeling, but are not dangerous. On the other hand, food allergy may be life-threatening. There are people who die each year due to food allergies. The distinction between allergy and side effects to food is important and only an experienced physician should make the diagnosis.

Common causes of food allergy vary with age. The following list includes the cause of allergy of near 90% of true food allergies: cow's milk, egg, sesame, soy, peanut, various nuts, fish. Food allergies can be classified according to the mechanism responsible for the reaction:

  • IgE-mediated Allergies: This group comprises the typical immediate allergic reactions that usually appear within minutes to one-two hours after exposure. In these cases the cutaneous test (prick test) is positive for food allergens. Allergies mediated by IgE antibody cause symptoms such as tingling, itching in the tongue or mouth, rash, redness, swelling of the mouth and around the mouth, runny nose, nasal congestion, red, swollen and teary eyes, sudden hoarseness, shortness of breath as sometimes even choking, abdominal pain and even blood pressure collapse and syncope. The most common presentation involves symptoms around the mouth (itching, rash and/or swelling). People who have asthma are at increased risk for reactions involving the airways, which are the most dangerous. It is mandatory to completely avoid exposure to the culprit food. The immediate treatment needed in case of these reactions is a function of the symptoms and their severity. When there is no involvement of the respiratory tract, care with antihistamine drugs may be enough. When there is respiratory tract involvement or dizziness or fainting, adrenaline should be injected immediately. Patients at risk must be equipped with an automatic adrenaline syringe (EpiPen). In any case, the patient must be taken immediately to the emergency room. Today there are treatments to induce "resistance" to food allergies that may prevent an allergic reaction to the culprit food or at least significantly raise the threshold for response (thus significantly decreasing the risk of an allergic reaction). These treatments are explained under the section "allergy treatment". A given percentage of children allergic to food spontaneously outgrow their allergies as they grow. This percentage depends on the cause. In case of a prolonged period of time with a total absence of reactions, an allergy evaluation must be done by an allergy specialist to confirm/rule out spontaneous development of tolerance to the allergen.


  • Non IgE-mediated Allergies: These allergies are not mediated by the allergy antibody (IgE), but by cells of the immune system. In these cases the skin tests (prick test) are negative. These allergies usually manifested by nausea/vomiting, abdominal pain, diarrhea with or without blood. Small children may show failure to thrive. In this group of allergies, the symptoms start usually late, days after the start of exposure to the culprit food, and the improvement after stopping the culprit food also takes some days. Diagnosis requires the cessation of the suspected cause and a significant improvement thereafter. Sometimes it is necessary to prove recurrence of symptoms after reinstituting the suspected cause to the diet. Food culprit avoidance is also very important in these cases. Most Non-IgE allergic children outgrow these allergies spontaneously as they grow. In case of a prolonged period of time with a total absence of reactions, an allergy evaluation must be done by an allergy specialist to confirm/rule out spontaneous development of tolerance to the allergen.