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By Emma Turner N.D.
Since the 1970?, the prevalence of diseases associated with allergy has been on the rise, particularly in developed countries1. Contributing factors include:
· Hereditary predisposition to allergies
· Chronic exposure to ?llergic·foods
· Environmental triggers such as house dust mites
· Poor diet of the mother during gestation and poor diet in early childhood. This may have a profound impact on physiology, and predispose to conditions associated with food hypersensitivities, including eczema, gastroenteropathies, and respiratory conditions such as asthma and hay fever2.
Patients who suffer from allergies and seek support for managing their condition keep health practitioners on their toes, as the presenting symptoms and body systems affected vary considerably from patient to patient. Body systems affected by allergic disease include2:
· Gastrointestinal tract
· Skin
· Respiratory system
· Neurological system which may lead to psychological symptoms
· Musculoskeletal system.
Food Allergy Vs Food Intolerance
Food allergies are often confused with food intolerances and vice versa. Food allergies develop when the body? immune system responds to food allergens via an immune mediated mechanism. This mechanism involves the production of IgE antibodies which react with the allergen, contributing to the release of compounds such as histamine. Common symptoms of an allergic reaction include swelling, itching, hives, and difficulty in breathing3.
There are four immunologic mechanisms that may contribute to allergic reactions2,4:
· Type I or IgE mediated hypersensitivity: initiated by an allergen binding to a specific IgE on the surface of a basophil or mast cell. There are two types of IgE-mediated hypersensitivity, atopic and non-atopic disorders. They include conditions such as urticaria, allergic rhinitis, and food allergy.
· Type II or antibody-mediated cytotoxic hypersensitivity: IgG or IgM antibodies bind to the cell bound antigen leading to cell death. This is typical of certain drug reactions in the body or mismatched blood transfusion reactions.
· Type III or antigen-antibody mediated immune complexes: these complexes are deposited together in tissue and activate complement. This causes an inflammatory response which may result in conditions such as rheumatoid arthritis.
· Type IV or cell-mediated immune response: T-cells rather than antibodies mediate this response. This mechanism is usually delayed and presents as a variety of clinical syndromes including allergic contact dermatitis.
Food intolerances are caused by non-immunologic mediated mechanisms (and may account for the majority of adverse food reactions that do not include reactions from foods that have been contaminated by micro-organisms)3.
Common preservatives and additives found in processed foods can also act as triggers for food intolerance or sensitivity, for example5:
· Sulfites (sodium sulfite 221): used as a preservative to reduce oxidative and enzymatic discoloration of foods. Sulfites are also used to sterilise equipment in fermentation processes to inhibit microorganisms.
· Monosodium glutamate (MSG 621): glutamate is an amino acid that naturally occurs in meat, fish, poultry, and milk. MSG is the sodium salt of glutamic acid (commonly referred to as glutamate). MSG is often used as a salt substitute and to enhance flavour and palatability of proteinaceous foods.
· Benzoic acid (210): naturally occurs in berries. Is used as an additive in food as a preservative due to its antiviral and antifungal properties.
Food intolerances may also be associated with inadequacies in digestion. Examples include gluten and lactose intolerance. In lactose intolerance, lactase is absent affecting the assimilation of dairy products in the digestive system3.
The Gastrointestinal Tract
Recurrent digestive symptoms can often be a reflection of the inefficiency of an individual? digestive tract. From a naturopathic perspective, the gastrointestinal tract is the focus of treatment for patients with allergies.
?eaky gut·is a term used to describe increased permeability of the intestinal mucosa. In combination with intestinal flora imbalance, poor enzyme function, and low gastric acidity (hypochlorhydria) digestive symptoms commonly present.
The immune system also has a dependant role on the lymphatic function of the gut. Disorders of the gastrointestinal tract may be related to immune system imbalance in the gut associated lymphoid tissue (GALT). GALT is made up of6:
· The appendix
· Peyer? patches
· Lymphoid follicles (mainly in the large bowel).
GALT (and other mucosal-associated lymphoid tissue) are covered by epithelium which contain membrane cells. These cells are responsible for the uptake of live and dead antigens from the gut lumen. Membrane cells are the main entry points for enteropathogenic infectious bacteria and viral agents6.
Correction of all of these aspects of the gastrointestinal tract will help to improve gut function which in turn will have a positive impact on immune function.
The Environment And Chemical Sensitivity
Idiopathic environmental intolerance (IEI), formerly known as multiple chemical sensitivities (MCS), is an acquired disorder characterised by adverse reactions attributed to exposure to low levels of certain substances under ordinary conditions7. These substances include8:
· Pesticides
· Fresh paint
· Cleaning agents
· Petrochemical-based products.
The most frequent symptoms associated with IEI are similar to MCS and include9:
· Fatigue
· Malaise
· Headache
· Light-headedness
· Hoarseness
· Rhinitis.
Although immunological dysfunction has been implicated in chemical sensitivity, other causes include respiratory tract inflammation and disorders such as porphyria (a group of disorders resulting from a disturbance in porphyrin metabolism)8,10.
Chronic conditions such as systemic lupus, chronic fatigue syndrome, and fibromyalgia have also been correlated with chemical sensitivity7.
Medical Tests For Allergy
There is no laboratory testing method that accurately diagnoses all ?otential·allergic reactions to food, including IgE mediated reactions of the immediate hypersensitivity type, such as food anaphylaxis. Avoidance and challenge with certain foods is commonly used to determine an individual? response to allergenic foods11.
Other methods of testing that are commonly used for allergy detection include:
· Skin prick test: an intra-cutaneous method of testing commonly used to test for type I immediate hypersensitivity reaction to antigens including dust mites, food, or pollen. This method is considered to best represent the biological sensitivity of an individual11,12.
· Radioallergosorbent test (RAST): used when direct skin testing is not possible due to skin irritation or disease. The test involves a known antigen to be mixed with a sample of the patient? serum. Any IgE specific antigen in the serum will attach to the conjugate. The amount of radioactivity taken up by the conjugate will determine the level of IgE in the patient? circulation13.
· Patch tests: a method used to test type IV delayed hypersensitivity reactions. Common allergens are applied under aluminium discs for two days and four days to the skin on the back. The skin is examined at two and four day intervals for any evidence of an eczematous reaction. If present, the result is indicative of type IV hypersensitivity to the allergen being tested12. Patch tests are used for defining contact sensitivities (especially dust mite in eczema).
· Serum IgE estimations: this test has limited value because a patient may have a positive skin prick or RAST test and have normal IgE levels. Serum IgE is helpful in detecting chronic infection, as elevated IgE may suggest parasitic infestation or contact sensitivity11.
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