What is an allergy?
An allergy is an abnormally high immune reaction to certain stimuli. Lots of people believe they have a food allergy or intolerance and seek allergy testing to identify which foods to avoid. People who have atopic conditions such as eczema, asthma or rhinitis (such as hay fever) are more likely to suffer from food allergies. These can either be immediate-type reactions linked to the antibody IgE, or more delayed reactions, usually involving gut symptoms. Food allergies are more common in children than adults, as children often outgrow their allergy.RELATED: RECOMMENDED PLANS FOR YOU
Diagnosing food allergy
Diagnosis starts with an allergy focused clinical history to identify all relevant symptoms and whether there are signs of immediate or delayed food allergies. Suspected immediate IgE mediated reactions are confirmed by skin prick testing or specific IgE allergy tests to the suspected foods, interpreted by a specialist in food allergy. The importance of having appropriate competencies to interpret the food allergy tests is highlighted in the RCPCH food allergy care pathway. There are currently no validated tests to diagnose delayed, non-IgE mediated food allergy, often incorrectly termed as food intolerance. The only common form of food intolerance (does not involve the immune system) seen in pre-school children is secondary lactose intolerance, due to loss of/ insufficient lactase. See the following article on the differences between lactose intolerance and cow’s milk allergy. Adults are more likely to suffer from a range of food intolerances, where they have a level of food that they can tolerate, above which they suffer with gut symptoms, as may occur in irritable bowel syndrome (IBS).
Diagnosis of delayed food allergy is achieved by eliminating the suspected allergens in foods for between 2-6 weeks to see if the symptoms get better, and then re-introducing them to see if the symptoms come back. If they do, this confirms the diagnosis. See the NICE food allergy guidelines and Milk Allergy in Primary care (MAP) guideline. There are no other validated methods for allergy testing. The NICE food allergy guidance states that some complementary or alternative health practitioners offer food allergy tests. These include tests such as applied kinesiology, hair analysis, vega tests and serum-specific IgG antibody tests but there is no evidence to suggest that they can reliably diagnose food allergy.
Beware of alternative tests for food allergy/ intolerance, including the following:
1. Applied Kinesiology (muscle testing)
The test gets the person to hold the suspected food, and muscle strength is then measured by applying pressure to the extended arm. It is believed that muscles in the body are sensitive to anything that is harmful, such as food allergens, and so become weakened. In young children, the parent may be used as an intermediary. Correction of imbalances in the body may involve crystals or acupuncture/ acupressure and can result in a long list of ‘food intolerances’. Kinesiologists are not qualified to diagnose or treat any medical condition, which includes allergies, yet worringly some practising kinesiologists state that their treatment can help with allergies, intolerances, reactions to foods, pollens, chemicals, anxiety, panic attacks, fears, phobias, stress, emotional issues, pain and sleep.
2. Vega testing (electrodermal test)
Vega testing is sometimes just referred to as food intolerance testing. The equipment used is a galvanometer, often referred to as a Vega machine, which measures electric currents to look at the body’s resistance to food allergens. The patient holds a cylinder in one hand while a small sensor is placed on the surface of the skin on either the fingers or toes, and the electric current is measured. Increased resistance to the current apparently indicates allergy to the food. The value on the galvanometer however is caused by the amount of contact and pressure applied by the technician.
A full food test involves around 100 different foods and will often results in a list of at least 20 different foods to avoid. Worryingly, the technician will usually provide nutritional information and guidance on eliminating these foods and possibly re-introducing them again. This is a role for a dietitian and exclusion of major food groups such as dairy, wheat and soy can result in nutritional deficiencies. An allergy focused clinical history may not be taken, in which case they would be unaware of whether they are dealing with IgE mediated allergies that carry a risk of life-threatening reactions. Re-introduction in such cases could potentially be fatal.
3. Hair analysis
A few strands of hair are tested for their mineral content. It is believed that if a harmful food is eaten, it will show up in the hair’s mineral makeup. Hair grows slowly (approximately 1cm per month) however, so hair does not reflect the current condition of the body. A wide range of suggested food intolerances usually result, which can include major food groups such as dairy. A list of deficiencies to various nutrients are also provided, including things for which there are no recommended intake levels, such as omega-3 fatty acids (DHA, EPA), glutamine, vanadium etc and therefore no way of identifying whether there is actually a deficiency.
4. IgG/ IgG4 allergy testing
This test involves a blood test to check for the antibody IgG, which is created by the body to fight certain allergenic foods. However, unlike IgE antibodies which are responsible for allergies, IgG is found in both allergic and non-allergic people. The production of IgG antibodies is thought to be a normal response to eating food, and often its presence reflects the fact that the food has been eaten recently. IgG has been shown to increase during successful research studies looking at food immunotherapy (regular introduction of small amounts of the food the person is allergic to, to try to get them to stop reacting to it). IgG testing usually results in a long list of food ‘intolerances’ which are likely to reflect the foods most commonly eaten, and hence would also have the most detrimental nutritional impact if advised to be excluded from the diet.
Food allergy testing and safety – summary
Children are more likely to have food allergies • The only allergy tests for immediate onset food allergies are skin prick testing of specific IgE blood tests • The only allergy tests for delayed onset food allergies are strict food exclusion for 2-6 weeks, followed by re-challenge • Multiple and major food group exclusion diets put people at risk of nutritional deficiencies and advice should be sought from a dietitian • Alternative allergy tests are not valid, are misleading and potentially dangerous.
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