Food Allergies & Sensitivities
By London Nutritionist Sylvia Hensher
Different Types Of Food Reactions
Type 1 Immune Reactions
The best known and well-studied form of food allergies is called a Type 1 immune reaction, also known as a classical food allergy. Type 1 food allergies occur in approximately only 2-5% of the population, mostly in children and are less frequent in adults. The reaction is immediate, usually appearing 15 – 30 minutes from the time of exposure to the offending food substance. Usually occurring in people who are genetically predisposed, the immune system begins creating a specific type of antibody called Immunoglobulin E (IgE) to certain foods. One side of the IgE antibody will recognise and bind to the allergic food. The other side of the antibody is attached to a specialised immune cell called a mast cell which is packed with histamine. Histamine is one of the chemicals that is released in the body as part of an allergic reaction, and which causes the itching, sneezing, wheezing, and swelling typical of allergic symptoms. Primed for action, the IgE antibody now patiently waits for re-exposure to food allergens.
So, when you eat the allergic food the next time, IgE antibodies hungrily latch onto the food. Instantaneously, histamine and other allergy-related chemicals are released from the mast cell, quickly bringing on the unwelcome symptoms of stomach cramping, diarrhoea, skin rashes, hives, swelling, wheezing or the most dreaded of all Type 1 reactions, anaphylaxis. Anaphylaxis is a severe, potentially life-threatening allergic reaction which causes your blood pressure to drop suddenly and your airways to narrow, blocking normal breathing. It requires immediate emergency medical attention.
Clinical approach: In Type 1 food reactions, offending foods are completely avoided and nutritional immune and digestive support provided.
Type 3 immune reactions
Type 3 immune reactions are much more commonly involved in food sensitivities than Type 1 reactions. In fact, 45-60% of the population has been reported as having delayed food allergies. A delayed food sensitivity also involves the immune system and occurs when your immune system creates an overabundance of antibody Immunoglobulin G (IgG) to a specific food. The IgG antibodies, instead of attaching to Mast cells, like IgE antibodies in Type 1 allergies, bind directly to the food as it enters the bloodstream, forming food allergens bound to antibodies circulating in the bloodstream. The allergic symptoms in Type 3 immune reactions are delayed in onset – appearing anywhere from a couple of hours to several days after consuming allergic foods. This delayed onset makes pinpointing the culprit food difficult. In this instance, laboratory testing may be useful.
Delayed food reactions may occur in any organ or tissue in the body and have been linked to over 100 allergic symptoms and well over 150 different medical diseases.
Clinical approach: In Type 3 immune reactions, it is important to identify food triggers, either through food exclusion tests or laboratory testing (more on this below).Depending on the symptoms, these foods are then excluded for a period of time, and then reintroduced on a rotational diet to avoid retriggering symptoms. In addition, nutritional immune and digestive support is provided.
Why Has the Incidence of Food Sensitivities Risen?
While there is no definitive evidence for the reason behind the rise in food allergies over the past decade or so, one of the most popular explanations is the “hygiene hypothesis.” Its main premise is that reduced microbial exposure, as a result of increased sanitation and cleaner lifestyles, has facilitated the rise in allergic disease in the Western world by affecting our immune system’s opportunity to develop standard immune responses. As a result, the immune system becomes prone to respond by reacting to otherwise harmless substances and we develop allergies.
We have two branches to our immune system that operate differently, and that need to balance each other for optimal health. The Th1 system of specialised white blood cells attack infected cells to help prevent infections from spreading. The Th2 system works by developing antibodies to microbes, thereby preventing the infection in the first place. Infants tend to use almost exclusively the Th2 system to protect themselves, and the Hygiene Hypothesis suggests that infants and young children need exposure to harmless microbes in order to “exercise” the Th1 system and make it strong. If that microbe exposure does not happen because the environment has been excessively sanitised, the Th1 system isn’t developed and the two systems become imbalanced. The Th2 system then becomes too powerful, creating an overreaction or allergic reaction to harmless substances like pollen and certain foods so that the infant or child is then more likely to develop allergies.
Testing For Food Sensitivities
Food Exclusion Test
This test is useful if there are up to 2 or 3 obvious suspect foods. These suspect foods are completely eliminated from your diet for two weeks, during which time symptom improvement or no change to symptoms is monitored. If symptoms remain unaltered or don’t improve, then the food you eliminated probably wasn’t’ the problem. If symptoms do improve during exclusion, the suspect foods are reintroduced (called a “challenge”) after the 2 week exclusion in a controlled manner (which your nutritionist will explain to you), to see whether symptoms remain the same or worsen. If your symptoms get worse after eating the food, try the process of elimination and challenge again to confirm the results. This is because it is possible that the first time was a coincidence. For example, perhaps the food you used for your challenge was greasy and upset your stomach, but you can tolerate the food in another form.
Keeping a food diary can help make your elimination diet more accurate and successful because keeping track of the food you eat and your symptoms allows you to look for patterns.
Sometimes a food exclusion test is not sufficient to identify foods suspected of causing adverse reactions. In this case, a blood test, which can help identify a much wider range of possible culprit foods may be useful. As discussed above, the underlying mechanisms for food sensitivities are not restricted to IgE-mediated reactions alone. For this reason, your nutritionist may suggest a test such as the Food Allergen Cellular Test, which can help identify both IgE mediated and non-IgE mediated reactions by measuring how cells themselves react to food allergens, in terms of the inflammatory substances they release.
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