Tests for allergies and intolerances

allergy testingWondering if your baby has an allergy or intolerance can be a stressful time. As well as dealing with unpleasant symptoms you then have an anxious wait while you get referred to a specialist GP or allergist. During this time you may be struggling to avoid certain foods in order to prevent your child’s symptoms from worsening.

You may have heard that there are places on the high street which can test for allergies within one day. But are they worth using and should you trust the results?

Many of the tests on the high street are based on complementary and alternative medicine, and not necessarily supported by scientific evidence to prove that they work, which is not the case for any testing done within the NHS.

The high street tests may sound believable and scientific, but have no proof that they work except from people who claim to have previously been diagnosed and feel much better. They can cost quite a lot of money and recommend avoiding lots of different foods or using herbal supplements. In the long term avoiding many foods which you believe you are allergic to, without any proof could lead to you not getting important vitamins and minerals as a result.

Tests which your doctor may request:

  • Skin prick test (SPT) – this is performed under medical supervision. A tiny bit of the food they think you are allergic to is placed on the skin, and the skin pricked. They are looking to see if a red lump (weal) a certain size appears, which indicates a specific type of allergy called an ‘IgE allergy’.
  • Blood tests (RAST) or ‘Specific IgE’ – this involves taking a blood sample and testing it with the suspect food and counting the number of ‘IgE’ antibodies produced in response.
  • Food challenge – small amounts of food are placed in the mouth and symptoms observed (under medical supervision).
  • Food exclusion and reintroduction – the suspect food is removed from the diet to see what effect this has on symptoms. If the symptoms improve then the food is re-introduced to see if the symptoms return.

High street tests available:

  • ‘IgG’ blood test – this uses scientific equipment to measure the amount of ‘IgG’ (an antibody which sounds similar to ‘IgE’ involved in ‘true allergy’, but completely different) produced to a suspect food. While it sounds a lot like the RAST/IgE tests mentioned above, this is completely different. Levels of ‘IgG’ do not reflect an allergy and they could even mask one.
  • Kinesiology (muscle testing) – This is based on a theory that certain foods can disrupt energy fields and cause muscle weakness, however there is no scientific evidence to support this and it could result in many different foods showing as ‘positive’ for an allergy.
  • Hair analysis – Testing a lock of hair in a laboratory for heavy metal levels or nutrient deficiencies. Whilst these tests may well check these, they have no relation to whether someone has an allergy or not.
  • Leucocytotoxic test – This sounds scientific. Blood is taken and the white blood cells from this are mixed with the allergen. If the white blood cells swell then this indicates an allergy. However there is no scientific evidence to suggest that this is linked to an allergy to that food.
  • VEGA/Electrodermal test – This is based on a theory that electromagnetic currents in the body change when presented with a food that the patient is ‘allergic’ to. However there is no scientific evidence to support the use of this testing.
  • Others – Other analysis which might be offered include blood analysis ‘while you wait’, stool sample analysis and tests on urine and saliva.

The decision you make is entirely up to you, however it is important to know that going through your GP ensures you will only be seen by trained professionals, using techniques which have good quality evidence to show that they work.

If you would rather get a diagnosis of an allergy done privately Allergy UK has a list of accredited specialists which can help.

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