Food allergy is common

It is probably less common than many people believe. Often claims of food allergy have been made to explain understood medical conditions. Some been based on impressionistic and anecdotal evidence and have not been evaluated scientifically. Part of the difficulty in estimating the prevalence of adverse reactions to food lies in confusion over the meaning of the term allergy. Commonly, any adverse effect due to food is attributed to an allergy. In fact, scientifically, most adverse reactions to food are not due to allergy, but to other mechanisms, such as a chemical reaction. An 'allergy' implies that there is an immune (body defence system) mechanism. It is now usual to refer to any adverse reaction to food as a food sensitivity; only some of these will be true allergies.

Community surveys have been conducted to assess the prevalence of food sensitivity as perceived by the participants. Estimates vary between 1 and 40 per cent but the true prevalence is likely to be small. Unfortunately, it is not possible to say how much smaller because this would require large-scale and expensive investigations involving detailed clinical histories, elimination diets where various foods are omitted from the diet, and challenges with the substances thought to cause the reactions. In many scientific studies patients have given histories consistent with sensitivities to particular foods, but when a food has been given in disguised form so that it is no longer recognisable, only a small proportion of patients actually show an adverse reaction. Nevertheless, sensitivities to various foods (for example, fruits and vegetables, nuts, fish) and food components (for example, salicylates, amines and sulphites - see SULPHUR-FREE DRIED FRUITS ARE HEALTHIER ) showing a wide range of symptoms (skin, gut, respiratory tract, psychological) have been established, and food sensitivity must be considered as a possibility when evaluating many medical disorders.