Allergy Testing
Allergy testing in the UK is not a straightforward process. It can be an extremely useful procedure provided that a history is taken to identify which tests would be most appropriate. However there are only very few recognised medical tests that can identify allergies and as a general rule these have been restricted to clinical laboratories or specialist centres.

Whilst the diagnosis of atopy or allergy by a qualified practitioner or specialist in allergy can be relatively easily made further tests are often required to confirm this. Such investigations are usually performed as a result of a medical referral to an NHS hospital. Waiting times can be substantial and the inconvenience associated with NHS referrals can be frustrating.

Types of Allergy Testing
There are only three types of medically approved tests for allergy:

1. Skin Prick testing
Suspected allergens are injected just under the surface of the skin (skin prick test) and the reaction is observed by a qualified nurse or doctor. As the reaction develops there is a zone of redness, the stronger the reaction the greater the zone. Skin testing is quite sensitive although not all allergies can be identified by this method.

2. Patch testing
Patch testing may be useful in cases of contact dermatitis. Test substances are usually applied to the skin covered by a patch and left in place for 48 hours. A positive reaction produces a small area of eczema. Again the reaction is observed by a qualified nurse of doctor.

3. RAST testing
RAST testing (radioallergosorbent test) detects the presence of an antibody called IgE in the blood. IgE is the substance that causes allergic reactions. IgE to an allergen is not normally detected in the blood and is only produced when a person becomes sensitised to a substance. Substances that cause allergy (called an allergen) produce a specific IgE that is unique to and will only react with it. This reaction between IgE and the allergen is like a lock and key. IgE, when combined with the allergen, causes cells to release chemicals (e.g. histamine), which cause the symptoms of allergy. A person may have specific IgE to more than one substance and may therefore be allergic to more than one substance.

Result for IgE testing are expressed as a grade that indicates how much IgE specific to the substance you tested for, is present in your blood. The higher the grade the more likely you are to be allergic. A negative test, however, does not 100% rule out an allergy. In a similar way a small proportion of allergy sufferers will still have a positive IgE test but will have outgrown their allergy or not yet developed symptoms.

RAST testing was traditionally only available through medical practitioners however, many pharmacies now offer this service. More recently BodyWATCH have released a testing kit that can be used at home, a sample of blood is sent to the laboratory for RAST testing.

Alternative Allergy testing
There are many alternative types of allergy testing and unfortunately few are accurate or recognised by the medical profession. Many of these alternative tests are performed in the high street and they can often be misleading as well as costly.

IgG Testing for Food Intolerance
Some commercial organisations offer "food intolerance" testing and measure IgG antibodies from a blood sample. There is no reliable method for determining food intolerance, as the mechanism of its reaction is not fully understood. IgG testing is inconclusive and its interpretation in relation to food intolerance has not been scientifically validated. Neither RAST testing nor IgG testing is useful for food intolerance reactions and such testing should be avoided.

Vega Testing
The Vega test is an electrical test described as bioenergetic regulatory technique. The machine measures conductivity with a Wheatstone circuit. Electrodes are connected to acupuncture points or held in the patient's hand. Different solutions are then placed in a metallic tray. The machine is then calibrated by placing a glass vial containing a toxic substance into the tray. The vial causes a reduction in electrical conductivity. Other substances are then placed into the tray and if they give a similar reading this is reported as an allergic or "sensitive" reaction.

This technique is widely used in health food stores however its value is unproven and there are no valid trials that will substantiate claims. Patients are often advised to eliminate foods from their diet by unqualified operators. This can often lead to a decline in patient health as without proper dietary advice deficiencies in the diet and subsequent nutritional status may occur. Elimination diets should only be prescribed by a qualified dietician or nutritionist and the BMA recommends that Vega testing should be avoided.

Leucocytotoxic Test
The Leucocytotoxic involves mixing the patient's white blood cells with an extract of specific food and then measuring the cells in different ways for evidence of some form of change. There are a high number of false positive and false negative reactions and the American Academy of Allergy concluded that there was no evidence that the test was effective for the diagnosis of food or inhalant allergy.

Hair analysis
Another form of testing is hair analysis. The hair can be analysed for the presence of toxic metals such as Lead, Mercury and Cadmium or low levels of Selenium, Zinc, Chromium, Manganese and Magnesium. Heavy metal poisoning is well recognised and documented in forensic science and hair analysis can indicate exposure to metals. However hair analysis as a means to diagnosing allergy, through methods such as "dowsing", have never been validated

Applied kinesiology
Samples of food are placed under the tongue or held in a glass container in the hand of the patient. The patient is then asked to push their free arm against that of the examiner. If an allergic response is detected this manifests as a reduced muscle response and the patient experiences difficulty in raising their arm. It has been difficult to find published evidence on this technique but in one study the technique failed to with stand up against a double blind study.

Conclusions
Studies of all the above alternative methods have been carried out at some stage by various scientific establishments and all have concluded that such tests used in the above manner are unscientific. Testing for allergy should only be done by an experienced person and preferably one that has been trained.