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Which allergy test should you choose?

The number of allergy sufferers are growing at an alarming rate in Britain.

And as they do, so too are the different methods of diagnosis.

Out of the scores of tests available on the market, finding the right one for your symptoms can be a minefield, particularly as medical opinion is bitterly divided over how accurate some tests really are.

To help you find the right test for your allergy, we've examined the main tests on the market - and asked an allergy expert to give their opinion on each one.


What is it used to diagnose? Food, skin and inhalant allergies.

What is it? A RAST (a radio-allergo-sorbent test) is a blood test carried out by your GP or a specialist allergy clinic. It looks for specific IgE antibodies - certain antibodies in our system that react to specific allergens which our immune system reacts to. These include dairy, nuts, molds, pet hairs or chemicals. The test can diagnose hundreds of different allergies, but your doctor is likely to test for just a few suspected allergies depending on the symptoms you display and your medical history.

What's involved? A doctor will take around five milliliters of blood from a vein in your arm using a syringe. The blood is sent off to a laboratory for analysis and the results are returned to your GP.

The verdict Maureen Jenkins, an allergy consultant from the charity Allergy UK, says: 'This is a very accurate test which has been scientifically proven to work. Although a patient may not be displaying symptoms, this test can detect whether there are any specific allergens (anything that triggers a reaction) in your body.

'A good allergy specialist has a deep knowledge of allergic conditions, the symptoms displayed and how your allergy will progress through time. The interpretation of the test is just as important as the test itself which is why it is vital to visit a qualified allergy specialist. '


What is it used to diagnose? Food, skin and inhalant allergies

What is it? This is a test which measures specific IgE antibodies in the cells of your skin. It looks for scores of food and environmental allergens such as nuts, seafood, dairy, fruit and wheat. It also tests for 'inhalant' or air allergies such as hay fever, mold spores and allergies to pets. It is one of the most common tests carried out by an allergy clinic or your GP.

What's involved? Skin prick testing

involves scratching the skin with a needle or lancet. A drop of the allergen prepared in liquid is placed on your arm. If you are allergic to the allergen, a 'weal' (blister-like swelling) will develop on your skin.

Verdict: Maureen Jenkins says: 'This test is between 90 and 100 per cent accurate. However, it is unable to predict a reaction to foods without any known symptoms. '

'The skill is in the interpretation of the results. Sometimes a person does not display symptoms, but tests positive for a certain allergy. It is therefore important that a highly qualified allergy specialist examines your symptoms, lifestyle and medical history before advising whether you should cut out certain foods. '


What is it used to diagnose? Skin allergies.

What is it?

Patch testing is a clinically proven test which looks for skin allergies - the type of reaction involving IgE antibodies which trigger classic allergic symptoms such as swelling. This test can also detect 'contact' allergies. This type of reaction is caused by certain cosmetics or chemicals which act as an irritant on your skin and trigger itching or a rash.

What's involved? You visit a hospital or allergy clinic as an outpatient where you are tested for 'environmental' allergies. This can range from deodrant, washing powder, certain metals, shampoo, cosmetics or clothing. Each sample is placed on your back and left in place for 48 hours. After 48 hours, you return to hospital and the patches are removed and a reading is taken.

The reaction is graded according to color and texture. This can vary from mild redness to swelling or water blisters. An 'irritant' reaction - the type of reaction triggered by cosmetics, chemicals or shampoos - develops immediately after the patch is placed on the skin and fades over the next day. An 'allergic' reaction - such as eczema - can take several hours to develop.

Verdict: Maureen Jenkins says: This is a very accurate test that is scientifically proven. However you already need to have regular symptoms so your allergy specialist has some idea of ​​what to test for.

'This type of test can detect scores of allergies. The skill comes from the interpretation of the test which is why it is important to visit a highly qualified allergy specialist. '

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