Lots of people think that allergy and food intolerance are just two expressions meaning the same thing. This even includes some Doctors! In fact, there is a big difference.

There is one thing allergies and food intolerances have in common: both can cause physical reactions, ranging from mild to severe. But that's pretty much where the similarity ends.

So what is the difference? It should become clear as soon as I give you the definitions.

An allergy is a physical reaction which is triggered by the immune system whenever a particular substance comes into contact with, or is ingested (eaten) by a susceptible individual. This includes the infamous peanut allergy, amongst others. Because the immune system is involved, a blood test can be used to test for an allergy.

A food intolerance is an inability to absorb or digest certain types of food, leading to a buildup of toxins which cause effects ranging from the inability to absorb other foods through to headaches, and many other possible symptoms. It does not involve the immune system, so it is difficult to devise a test, particularly as different individuals may react in different ways. In fact, the only test I know of for anything that might be described as food intolerance is the one given to test for celiac disease, and even this is not entirely accurate.

You might think there is little point in making the distinction. So what if the immune system is involved? It's up to the doctors to do the diagnosis - they must know what they are doing.

If only life were that simple.

It's sad, but the medical profession is so wedded to their little test tubes that many of them deny that food intolerance exists, because they cannot detect a reaction from the immune system. Others are happy to take your money for spurious tests that will not detect anything, for example:

• Skin test: The classic test for immune response. Good for discovering if you have an allergy, but useless for pinpointing intolerance.
• Tongue test: A modification of the skin test, again only suitable for discovering allergies, rather than food intolerance.
• RAST test (radioallergosorbent test): A blood test. Another test suitable for testing for allergies, but not for intolerance.
• Cytotoxic test: Attractive in theory, but disappointing in practice. Do not take this test as the results are unreliable, with many false positives.
• Hair test: A test for mineral deficiencies offered as a way of diagnosing possible food intolerance. However, there does not seem to be any link between mineral deficiency and food intolerance!
• Blood mineral analysis: Again, mineral levels are tested, but the link between mineral deficiencies and any food intolerance has not been demonstrated.
• Blood (antibody) test: Any food antibodies found in the blood will demonstrate a food allergy. However, no antibody does not equal no food intolerance.

None of these tests are of any value in finding out if you are food intolerant or not. The only reliable way of discovering what, if any, food intolerances you may have is by means of an exclusion diet.