A food allergy is an immune system-mediated adverse food reaction. In other words, food allergies happen when the body mistakenly reacts to a food as if it is harmful to you. The food itself isn’t dangerous; it’s the way your body reacts to the food. Food allergies can be further categorized into IgE-mediated reactions and non-IgE-mediated reactions. IgE-mediated reactions can lead to anaphylaxis which is an acute and severe allergic reaction that includes symptoms of hives and swelling, respiratory distress, immediate vomiting and diarrhea and low blood pressure. These reactions can happen in both children and adults and can be life threatening. These reactions often happen quickly; within 10-60 minutes following ingestion of the offending food. It is important to differentiate a true food allergy from non-IgE mediated adverse food reactions. Non-immune mediated adverse food reactions include food intolerance or toxic and/or pharmacologic responses to food. These responses to food are quite different from immune-mediated food allergy and typically are not life-threatening. For example, a pharmacologic response would include an increased heart rate from caffeine.
The prevalence of food allergies have been increasing over the past 25 years. Approximately 6-8% of children and 3-4% of adults have a food allergy. Milk, egg, peanut, soybean, wheat, tree nuts, fish and shellfish account for 90% of food allergies in children. Peanut, tree nuts, fish and shellfish account for 90% of food allergies in adults. Individuals who have a food allergy need to practice strict avoidance of that food. This includes reading the ingredient list of foods with each purchase as ingredients can change without notice. Individuals with food allergies should also be aware of the potential risk of cross-contamination and potential accidental exposure to the food both at home and when eating out. Auto-injectable epinephrine needs to be available in case the food-allergic individual is accidently exposed to the food and has an anaphylactic reaction. Your allergist or pharmacist can instruct you on how to use the auto-injectables. Medical alert bracelets are also recommended for individuals with food allergies.
The prevention of food allergies has been an area of interest over the years. Historically, expert opinion has recommended delayed introduction of highly allergenic foods.1 However, in 2008, the American Academy of Pediatrics guidelines on food allergy prevention were revised and now state that there is no convincing evidence that delayed introduction of solid foods beyond 4-6 months has a protective effect. 2 Furthermore, there appears to be no evidence for the protective effect of dietary maternal restrictions during pregnancy and lactation. 2 So unless the mom has food allergies, there is no reason to eliminate certain foods such as peanuts, tree nuts, milk, eggs, wheat, soy, fish or shellfish.
The debate over early or delayed introduction of highly allergenic foods continues and some recent evidence suggests that earlier introduction of these foods may actually be of benefit to infants. For example, a recent study out of Melbourne, Australia with a cohort of 2589 infants suggested that introducing egg into the diet at a later age (10-12 months of age and after 12 months) was associated with higher risks of egg allergy in these infants. 1 The data from this study suggested that introducing cooked egg at 4-6 months might actually protect against egg allergy. 1However, the results of this study must be confirmed by further studies before any changes in infant feeding guidelines can be recommended. The current infant feeding guidelines as outlined by Health Canada recommend exclusive breastfeeding for the first 6 months.
The Canadian Society of Allergy and Clinical Immunology (CSACI) and Canadian Pediatric Society (CPS) are in the process of publishing a joint statement regarding food introduction to infants. In Nova Scotia a good reference on food introduction for parents is Loving Care which is available from your local public health nurse or online3. If you are concerned about food allergies, talk to your family physician as a referral to an allergist may be warranted.
Allen KJ, et al. Can early introduction of egg prevent egg allergy in infants? A population-based study. J Allergy Clin Immunol 2010; 126: 807-13.
Greer FR, Sicherer SH, Burks AW. Effects of early nutritional interventions on the development of atopic disease in infants and children: the role of maternal dietary restriction, breastfeeding, timing of introduction of complementary foods, and hydrolyzed formulas. Pediatrics 2008; 121: 183-91.
3. Parent Health Education Resource Working Group. Loving Care: 6 to 12 Months. [Halifax]: Nova Scotia Department of Health and Wellness, 2012.
Food Allergy Awareness Month: Are You Aware?
by Anna-Claire Coleman MD, FRCPC, PGY6 Pediatric Allergy & Immunology, Dalhousie UniversityLori Connors, MD, FRCPC, Assistant Professor, Dalhousie University