A Type I immediate IgE hypersensitivity immune response is more commonly known as a food allergy and this reaction typically occurs very quickly (within minutes to hours) after eating an offending food, with symptoms ranging from mild to severe.

The mechanism which takes place in an IgE allergic reaction is initiated by these specific antibodies, by the activation of mast cells that line the body surfaces. Once activated, they initiate the allergic cascade, stimulating inflammatory reactions by secreting chemical mediators such as histamine and cytokines.

Many are aware of food allergies causing anaphylaxis (the most common example being peanuts), but they may also experience itchy lips/tongue/throat, stuffy nose, headaches, stomach pain, diarrhoea, gas, bloating, skin reactions, and sudden fatigue.

Most people often know their ‘trigger foods’ because when the reaction occurs, it is so quick and happens soon after eating food. However, sometimes it isn’t always obvious, particularly with people who have multiple allergies. In these instances testing can be very useful and is done by measuring specific IgE antibodies in the blood to the suspected foods and food panels.

NB. IgE allergy is not something that we currently test for and will not be identified by our IgG mediated food intolerance tests. If an individual suspects that they may have an IgE allergy, then they should consult their GP to be tested for this.

The binding of IgG antibodies with a bacterial or viral antigen, results in antigen coating and the formation of an immune complex. This consequently triggers further immune responses, including the release of pro-inflammatory cytokines, with the developing inflammation being accompanied by mechanical damage to the surrounding tissues.

The activity of IgG antibodies is identical as far as food antigens are concerned. As the food components in patients with increased intestinal permeability (leaky gut syndrome) enter the bloodstream from the intestinal lumen on a continuous basis, the immune mechanisms undergo constant activation. This can eventually overload the immune system’s ability to clear such complexes efficiently, which results in chronic inflammation.

Elevated levels of IgG antibodies to food antigens have been observed in diseases associated with increased intestinal barrier dysfunction; in particular, IgA deficiency, coeliac disease and inflammatory bowel disease. The controversy surrounding food IgG testing relates to the significance of food IgG antibodies in the pathogenesis and diagnosis of food intolerance and a number of chronic illnesses, including IBD, IBS, migraine and arthritis. However, a number of clinical studies to date, have in fact been supportive of a role for food IgG testing in certain illnesses.

The clinical manifestations of chronic IgG-mediated reactions are determined by the target tissue or organ to which the immune complexes composed of IgG antibodies and the specific food antigens are transported within the bloodstream. High levels of the complexes accompany such dissimilar disease entities as migraine, irritable bowel syndrome, chronic fatigue syndrome and Crohn’s disease. The protective nature of IgG antibodies becomes a property that severely burdens and disturbs the body’s homoeostasis. This type of hypersensitivity is the so-called delayed allergy or food intolerance. The signs and symptoms develop within 8 to 72 hours after ingestion of the offending food.

Often, patients do not associate a given symptom with the food they ate, especially because of the lack of the characteristic “allergic” symptoms. This is the fundamental argument that highlights the controversial nature of this type III food allergy.

We use specific food extracts to identify the corresponding level of circulating IgG antibodies to these potential antigens and can therefore detect foods to which the immune system is reacting. This can help to guide individuals towards making informed dietary changes with the support of a qualified nutritional therapist, in order to potentially alleviate unpleasant symptoms that they may be experiencing as a result of an IgG-mediated food intolerance.

Classic food intolerances are known as non-immune mediated reactions. This means that, unlike IgG food intolerance or a classic allergy reaction, that the immune system is not involved. Some examples of this type of intolerance include enzyme deficiencies, such as lactose intolerance and histamine intolerance. Both these intolerances are caused by the absence of the enzymes lactase and diamine oxidase (DAO) respectively.

Taking lactose intolerance as an example, lactase, normally secreted in the small intestine, is not produced which means that lactose (the primary sugar in milk) cannot be metabolized into its absorbable component monosaccharides, glucose and galactose. Undigested lactose cannot therefore be absorbed across the small intestinal epithelium and as a result, passes into the colon, where gut bacteria metabolize it into carbon dioxide, hydrogen and water. The characteristic symptoms of lactose intolerance are bloating, flatulence, abdominal cramping, and diarrhoea.

Most infants have sufficiently high activity levels of lactase at birth, which for most populations decreases at mid-childhood (about 5 years of age). This reduction is more pronounced in individuals from certain ethnic groups, which would explain the higher prevalence of lactose tolerance within individuals from these specific backgrounds. High lactase levels continue into adulthood in a few ethnic populations however, such as Northern European Caucasians, presumably as an adaptation to the widespread historical use of dairy products in these cultures.

It has been shown however, that individuals with lactose intolerance appear to tolerate yogurt and acidophilus milk better than other dairy products, despite these products containing substantial amounts of lactose. This may be due to fermented products having an inherent lactase activity, which is partially able to survive digestive processes and aid in the metabolism of lactose in the small intestine.

Fructose intolerance is similar in nature to lactose intolerance, in the sense that it occurs when the body’s digestive system doesn’t absorb fructose properly. Symptoms can be quite debilitating, including abdominal pain, diarrhoea and flatulence. The cause is not due to an enzyme deficiency and rather relates to deficient carriers in the intestine, which inhibits absorption, as well as an imbalance in the bowel flora.

Additives, both natural and artificial used to flavour and preserve food, such as sodium benzoate, sulphites (a preservative found in dried fruit and vegetables) and monosodium glutamate can cause varied symptoms including asthma, hives, dizziness, sweating and even nausea/vomiting and diarrhoea.

Other food intolerances that fall into the non-immune mediated category include chemical or pharmacological reactions. Vasoactive amines such as histamine (see Histamine Intolerance, DAO), tyramine and phenylethylamine found in chocolate, have been found to contribute to symptoms such as migraine in some individuals. Salicylate sensitivity, another pharmacological reaction which has been estimated to affect up to 5% of adults, can cause a variety of symptoms including stomach pain, tinnitus, fatigue, sinusitis etc. Salicylates are naturally present in fruit, vegetables, herbs, spices and condiments, nuts and seeds. Aspirin (Sodium Salicylate) is a well-known non-steroidal anti-inflammatory drug (NSAID) that may potentiate some acute allergies and causes adverse immunological reactions which have now been found to be immunological in nature are collectively referred to as aspirin intolerance.

NB. Lactose intolerance is not something that we currently test for and will not be identified by our IgG mediated food intolerance tests. If an individual suspects that they may have lactose intolerance, then they should consult their GP to be tested for this.