ALLERGY: FOODS

March 30th, 2009

Opinion among doctors and experts as to the degree of cross-reaction between foods varies widely; you will often encounter differing (sometimes conflicting) advice on which foods cross-react.

Foods, as all living things, are classified biologically into groups and sub-groups according to their inter-relationships. These categories include ‘family’ and ‘sub-family’ groupings. It is argued that cross-reaction is more likely to occur within a food family, and diets may be planned and managed on this basis. If you are on a rotation diet, for instance, you will often be advised to leave an interval of two days or more between eating foods that belong to the same family. This can be quite restrictive.

In practice, the family model is not always helpful. Some families, such as the legume family, which includes peas, beans, pulses and peanuts, are very broad. Some foods within such a family are very distantly related, and cross-reaction can be rare. Sometimes cross-reaction only occurs consistently within sub-families. The grass family includes the wheat sub-family, the corn sub-family, and the rice subfamily, and cross-reaction often occurs within the sub-families, but less commonly between them. If you react to wheat, for example, you are more likely to cross-react to oats, which is part of its sub-family, than to rice, which is related but belongs to a separate sub-family.

Moreover, in the case of some highly allergenic foods, such as fish, birds’ eggs, birds and nuts, some people appear to react to all types of the food, irrespective of the family from which they come, and managing the families of these food types has no relevance at all for these individuals.

Like many aspects of allergy and sensitivity, the cross-reaction of foods can be very confusing, and you will probably have to work out for yourself, with expert guidance, what you tolerate and what causes cross-reaction in you.

The best way to deal with the question of food cross-reaction is probably to adopt a strict and conservative approach initially, when you are first working out what you react to. On an elimination diet (or on a rotation diet, if this is advised), start by being careful about the food families, and then relax gradually in order to find out what you can tolerate. You may not need to observe the families at all eventually. (For full advice on planning diets, a full list of food families.

Some foods contain moulds and can cause cross-reaction. Oils and terpenes in foods can also cause cross-reaction. Some foods cross-react with pollen.