Food Allergy: What You Need to Know

Stephanie A. Leonard, MD


November 15, 2010

In This Article

Final Perspective and Clinical Recommendations

Food allergies are on the rise in westernized countries for reasons that we do not completely understand. The rise in food allergies parallels the increase in other atopic diseases. No cure currently exists for food allergy. Management consists of education, avoidance of allergens, and appropriate response to acute reactions.

The most common food allergies in childhood are milk, egg, and peanut. Most children outgrow their milk and egg allergies, whereas peanut allergy is more likely to be lifelong. The most common food allergies in adulthood are peanut, tree nuts, fish, and shellfish. Although peanut is the allergen most often associated with severe or fatal reactions, any food has the potential to cause anaphylaxis.

Patient history is the most important diagnostic tool in the evaluation of food allergies. Skin testing and specific IgE testing provide additional information and can be used to monitor the status of food allergies over time or determine if an oral food challenge is appropriate. An oral food challenge is the gold standard for diagnosis of food allergy; however, this test is typically only used when the diagnosis is in question or if it is believed that the food allergy has been outgrown.

Food-allergic individuals and their caretakers must be aware of hidden allergens and cross-contact at every meal and be prepared to treat if an allergen is accidentally ingested. The amount of food required to trigger a reaction or the severity of a reaction cannot be predicted. Intramuscular epinephrine and antihistamines are the mainstays of treating acute allergic reactions. Research into curative or mitigating food allergy therapies is ongoing.

Recommendations for Practitioners

  1. Delaying of potentially allergenic foods until 1, 2, or 3 years of age has not been shown to prevent food allergies. In 2008, the American Academy of Pediatrics amended their earlier position and no longer recommends avoidance of such foods as a preventive measure.

  2. Food allergic patients, especially those with a new diagnosis, should be seen by an allergist for complete work-up, education, and management. Children can outgrow their food allergies, and yearly monitoring is warranted.

  3. Specific food IgE levels can be measured after careful history-taking identifies potential allergens. The focus should be on foods ingested within 2 hours leading up to an acute reaction or foods that appear to consistently exacerbate eczema.

  4. Specific food IgE testing panels are not recommended because of the occurrence of false positives and the potential for foods that an individual has been tolerating to be unnecessarily removed from their diet.

  5. Removing a previously tolerated food from a patient's diet solely on the basis of an elevated specific IgE can put the patient at risk for developing an actual clinical allergy to that food.

  6. An undetectable specific food IgE level is not a guarantee that an individual is not allergic. If the history is suggestive, skin testing should be performed (and possibly an oral food challenge as well) before the food is ingested again.

  7. Specific food IgE levels help to predict the likelihood of reactivity but not the type or severity of reaction. The significance of the levels varies among foods, so they are not comparable.

  8. Food allergic individuals should carry 2 self-injectable epinephrine devices and antihistamine at all times in case of emergency. Self-injectable epinephrine devices should be renewed once a year.

  9. Epinephrine given for an allergic reaction is most effective when administered intramuscularly into the thigh muscle.

  10. Biphasic reactions can occur in up to 20% of anaphylactic cases, and monitoring patients for 4-6 hours after a food allergy reaction is recommended.

  11. Corticosteroids are not useful in the acute management of an allergic reaction because of slow onset, but they might prevent biphasic or protracted reactions.

  12. Adolescents and patients with a history of asthma are at higher risk for fatal anaphylaxis and require additional education. Delay of epinephrine is also a risk factor for fatal anaphylaxis.

  13. Food allergies have a profound effect on quality of life, and support groups and Websites of food allergy organizations (such as the Food Allergy and Anaphylaxis Network, or FAAN) can be useful.


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