Food Allergy and Food Intolerance Testing
The use of complementary and alternative medicine to diagnose food allergy and intolerance is growing fast. There are many types of ‘tests’ available on the high street and on the internet and it is difficult to know what is reliable and scientifically sound.
This fact sheet looks at various tests available and discusses the scientific background or ‘evidence’ behind them.
In this fact sheet:
- Conventional Food Allergy Testing
- Food challenges
- Alternative food allergy tests
- Download this information as a PDF
Conventional Food Allergy Testing
These tests are evidence-based and performed by registered health professionals:
Skin prick test
A small amount of diluted allergen (suspected protein that person is allergic to) is placed on the skin and the skin is then pricked. If a small swollen lump or ‘weal’ appears, in conjunction with a detailed clinical history, an IgE mediated food allergy may be diagnosed. This test is only performed under medical supervision.
A specific IgE test, formally known as Radio Allergo Sorbent Test (RAST) is carried out by measuring the amount of IgE antibodies to a suspect food in the blood. The results are interpreted with a detailed clinical history to give a diagnosis of IgE mediated food allergy. This blood test can be organised by your GP or hospital clinician.
There are commercial companies who offer a similar blood test called MAST (Multi-Allergen Screening Test). However, as they do not have your detailed clinical history, it is difficult for commercial companies give an accurate diagnosis.
The suspect foods are given orally (in the mouth) in small amounts and the quantity is built up gradually whilst symptoms are observed. The food may be given openly or ‘blinded’ (when people are unaware which food they are eating). Again, this should only be performed under medical supervision where medical facilities and resuscitation equipment are available.
Food exclusion and reintroduction
The suspected food or foods are excluded for a period of time and symptoms observed and recorded. If symptoms improve then the suspect food is reintroduced. If symptoms return then this would indicate that there is a problem with that particular food.
This can be very time consuming and is best carried out under the supervision of a registered dietitian, especially if children are involved. It is important to ensure a well balanced nutritional intake during the test period and in the design of a diet where major food groups are excluded (e.g. dairy or wheat).
Alternative food allergy tests
There are also many commercially available tests that claim they can diagnose food hypersensitivity. These should be avoided as they have no scientific basis and can be harmful when multiple foods are excluded without reason and if they are not reintroduced under guidance of a dietitian.
IgG blood test
This blood test looks at IgG antibodies present in the blood. It’s claimed that an increase in IgG to a certain food indicates an intolerance to that food. At present there is no convincing evidence to support this test, and it’s not recommended as a diagnostic tool.
This is based on the idea that certain foods cause an energy imbalance in the body which is detected by testing the response of the muscle. The client holds the suspect food which is in a glass vial and the therapist tests the muscle response. The result can lead to many foods being eliminated from the diet however research studies show that this test is no better than chance and is therfore not recommended.
A small lock of hair is sent off to a laboratory and the energy fields in the hair are scanned. The results are compared to other established data to identify a food hypersensitivity. Although this is used in testing for recreational drug use as well as lead and mercury poisoning, its use in allergy testing is unproven and has no scientific basis.
Leucocytotoxic or Cytotoxic test
This is a blood test where the white blood cells are mixed with the suspect food and if they swell this would indicate a problem with that food. There is no rational scientific basis for this test.
The pulse is taken before eating the suspect food and then 15 minutes afterwards. An increase of ten beats per minute would indicate food intolerance. Research shows there is no connection between the increased pulse and food intolerance and is therefore not recommended.
Electrodermal (Vega) test
This test measures the electromagnetic conductivity in the body. An offending food will show a dip in the electromagnetic conductivity. Research studies show that this test is no better than chance.
These alternative allergy tests may suggest long lists of foods to be excluded from the diet unnecessarily. Excluding a major food group e.g. wheat or milk, or a combination of different foods, creates many practical difficulties. Without good nutritional advice, a restricted diet can lead to severe nutritional deficiencies and malnutrition.
If a food allergy is suspected, you should seek medical advice and discuss the use of evidence-based,
conventional allergy testing. Alternative allergy testing should be avoided as it has no scientific basis.
Dietitians can give you the correct nutritional advice and ensure a well-balanced nutritional intake which will be tasty, varied and culturally acceptable.
Children should not follow a restricted diet unless supervised by a dietitian as they require a well-balanced diet to ensure adequate growth and development.
Download this information as a PDF
This Food Factsheet is a public service of The British Dietetic Association (BDA) intended for information only. It is not a substitute for proper medical diagnosis or dietary advice given by a dietitian. If you need to see a dietitian, visit your GP or a private dietitian.
Written by Liane Reeves, Dietitian.
© BDA December 2017. Review date December 2020.