|Food Allergies Part II: Testing for Food Allergies, Elimination/Challenge Diets and Food Intolerance
In Part I, we went over the two main types of allergic reactions to foods; called immediate and delayed hypersensitivity reactions. To recap: these reactions each have their own antibody, a type of white blood cell called an immunoglobulin. IgE (or immunoglobulin E) reactions occur immediately following ingestion of an allergenic food, while IgG reactions can take hours or days to show symptoms.
Most immune-type food reactions are actually IgG reactions. There is a good side to this as IgG allergies do not generally cause the same severe symptoms we associate with IgE reactions – symptoms such as hives or airway constriction. On the other hand, when symptoms don’t closely follow food intake, it can be quite difficult to decide which foods are causing the problem.
Additionally, there is a third type of food reaction called intolerance, which is not the result of an immune reaction at all. These are typically to foods such as artificial colours, flavour, or preservatives, but can also happen with foods such as cheese, chocolate, or strawberries. Celiac disease, which arises from intolerance to gluten foods (wheat, barley, rye, millet and sometimes oats) is often in this category and can be very difficult to diagnose in its early stages.
So how do we sort this all out? The first thing I tell new parents who call my office asking about food allergies is that we need to deal with the serious stuff first. If they notice their child has a reaction within a few minutes of eating a food – such as wheezing, a stuffy nose or hives – then it’s best for them to see a pediatric allergist, find out if these are IgE allergies (usually with either a skin prick or RAST blood test), and treat them. This is particularly true if the child is less than 3 years old.
On the other hand, if the child has less severe symptoms, say frequent colds, or eczema, or behaviour changes, then we can proceed with allergen testing or an elimination/challenge diet to sort out dietary reactions that way. The best starting point is always a sound medical history – when the problem started, what happened at that time, what makes the problem better or worse and so on. Frequently, getting this information in itself will give important clues to the source of the problem, which may or may not be a food allergy.
From this history, we can then make a decision whether to suspect one or two foods in particular (easier when the child has been newly introduced to solid food). In this case, we would eliminate the food completely for a short period, usually 2-3 weeks, then re-introduce it. Often the symptoms clear during the elimination phase itself, which gives us an answer. Sometimes the challenge phase brings on the same or new symptoms, which also gives us an answer.
When the picture isn’t as clear, or in older children, we can do an elimination/challenge diet eliminating all of the most common food allergens for 3-4 weeks, or we can test the blood for IgG allergens. A common elimination diet would remove the most common offending foods in the Western diet: dairy, gluten, eggs, corn and soy. Because these diets can be a significant change from normal family eating habits, we spend time discussing such topics as assembling shopping lists, learning to read labels and meal planning to maintain allergen-free food during the period of elimination. Challenges, as well, need to be carefully planned so that we can be reasonably certain that any symptoms that arise are because of the food allergy we are trying to determine. Still, when done carefully, elimination/challenge can be a very effective way of determining whether symptoms are due to a specific food.
Another option your ND can choose is IgG testing, usually though a blood sample. This is relatively quick and painless and can save parents a lot of time and energy having to change many of their dietary habits at once. The technical name of the method they use is ELISA testing, as is becoming increasingly accepted as a useful way to test for food allergies. From this information, your ND can plan an individualized elimination and/or rotation diet which can help to alleviate or abate many chronic long-term health problems such as eczema, asthma, ADHD and headaches.
The best news about IgG food allergies is that they may not be for life. Often, working to improve digestive health and immunity can also improve the body’s innate ability to distinguish harmless substances, such as foods, from invaders, such as bacteria and viruses. The key is to try to heal the digestive system with botanical and nutritional therapies, while we remove the foods that may be driving the allergy-type symptoms. Over the long term, once the inflammation is gone and the microbes that line the gut are back in balance, often foods can be re-introduced and will no longer cause reactions.
For more information:
Brostoff J, Gamlin L. Food Allergies and Food Intolerances: the Complete Guide to their Identificaiton and Treatment. Rochester, Vermont: Healing Arts Press, 2000.
Lipski, L. Digsetive Wellness, 3rd ed. New York: MCGraw Hill, 2005.
For additional information about Dr. Marianne Trevorrow
ND please visit: www.drmarianne.ca