In testing for allergy, it is important that the tests used have been shown to be useful – that is, there is evidence that a particular test is reliable and accurate. With ongoing research into allergy and its diagnosis, we are learning more about the science underlying allergy and much of this work is improving the way health professionals can look after patients with allergies.
Nonetheless, many people with allergies consult alternative practitioners for help. Patients may seek help in the diagnosis and management of non-allergic symptoms, such as muscle tension, headache and migraine, non-specific bowel symptoms, fatigue and depression. While these symptoms are very troublesome to the patient, there is no evidence that they are due to an ‘allergy’ to a food in the conventional sense of the word. Some alternative practitioners may recommend the use of non-conventional tests. These tests are not considered to be relevant, standardised or repeatable and therefore have no place in the diagnosis of allergy. Such tests include:
- Applied Kinesiology (measures changes in muscle strength before and after exposure to an allergen)
- Auricular Cardiac Reflex Method (measures strongest pulse at wrist)
- Blood tests for IgG antibody
- Hair Analysis
- Cytotoxic Testing (which assesses the size and shape of white blood cells after exposure to foods)
- Vega Testing (measures the electromagnetic fields produced by the sufferer when an allergen is brought near the patient)
IgG Blood Tests
IgG blood tests measure IgG antibodies. These are very different to IgE antibodies (which are known to be vital in immediate-type allergy). IgG antibodies are produced by the immune system in response to exposure to a variety of external proteins, including foods and pollens. Their presence is simply a result of a person being exposed to these proteins, and not because these proteins are causing a symptom or disease. There is no reproducible, high quality evidence that IgG antibodies are involved in food allergy or intolerance, or that they can cause symptoms. (The only exception is that IgG antibodies against gluten might be important in some people with coeliac disease.)
Unfortunately, many practitioners including some doctors continue to offer these forms of testing, which are often costly and give misleading results. In some countries, governments have taken legal action against companies offering IgG testing due to unsubstantiated claims that the tests are useful in the management of food allergies and intolerances.
What are the Problems with Unproven Tests?
- They often cost significant amounts of money, as they are not available on the NHS (because they are unhelpful in the diagnosis of allergies).
- Patients may receive incorrect advice as to changes in their diet, which can cause significant inconvenience and, in some cases, risk malnutrition and affect long-term health.
- The use of effective diagnostic techniques and treatments may be delayed, resulting in the patient suffering due to poorly controlled allergic disease.
- Non-conventional tests may result in advice being given as to unnecessary environmental and chemical avoidance. Such misdiagnosis is misleading to the patient and can create a false sense of security.
If in doubt, always ask to see evidence of the results of approved clinical trials using these tests. Find out how the tests work, if there are any side effects and if the results have been published in medical journals. Finally, we would recommend discussing any concerns you may have with your GP, or you can contact the Allergy UK Helpline for advice.
Can We Test For Food Intolerance?
IgG blood tests are often used to diagnose food intolerances. However, as discussed above, the results often only indicate that a person has eaten a food, not that a particular food is causing symptoms. The data supporting use of IgG tests is limited and not reliable. Food intolerance can occur in various ways, and we still do not understand the causes of patients' symptoms.
Therefore, the ‘gold standard’ test for food intolerance remains the elimination and challenge diet (see Food Intolerance factsheet), which should always take place under the supervision of an approved dietician.