The symptoms of food allergy are hives, nose stuffiness, asthma, eczema, vomiting, diarrhea, gas, or migraine headaches. We know through experience that fish, shellfish, berries, nuts, and chocolate frequently cause hives, while cereals, milk, egg, or meat more often cause nose stuffiness and asthma.

A food allergy is usually diagnosed clinically with a diet diary, an elimination diet, or a provocative diet. Skin testing has little value in diagnosing food allergy.

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The offending element in wheat is the main protein, commonly known as gluten. In fact gluten is a mixture of dozens of different proteins, which fall into two main types, the glutenins and the gliadins. The part, or parts, of these proteins that produce coeliac disease have still not been identified.

Exactly what goes wrong in coeliac disease is not entirely clear, and the disease seems to be quite complex. There is definitely an inherited component because coeliac disease runs in families. And the immune system is involved in some way, as shown by the large numbers of immune cells found in the coeliac’s gut lining.

The most widely accepted theory at present is that one or more components of gluten are lectins and that they specifically bind to carbohydrate markers on cells in the gut wall of coeliacs. We all have these carbohydrate markers, and they are determined genetically. The theory is that coeliacs inherit a particular type of marker molecule on the surface of their cells, which happens to be bound by the lectins in gluten. The combination of lectin-and-marker looks like an unwelcome alien to the immune system, which then proceeds to make antibodies against it. In the relentless war against the bound lectin, the immune system causes severe damage to the gut lining, which is then unable to function properly. The available evidence suggests that this theory may be correct in broad outline, but the details still need to be filled in.

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