Royal Prince Alfred Hospital Royal Prince Alfred Hospital
Allergy Unit

Student Research


The role of natural salicylates in food intolerance

by
Anne R Swain
Doctor of Philosophy (PhD), The University of Sydney
Supervisors: A. Stewart Truswell, Robert Loblay
February 1988

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Abstract from PhD thesis

During the 1960's and 1970's several authors reported that manipulation of diet to exclude certain additives and natural chemical substances led to apparent clinical benefit in a number of conditions, however, available diets were largely empirical. In April 1977, the present study commenced with the development of an elimination diet, in order to investigate the role of food in recurrent idiopathic urticaria/angioedema. Stable asymptomatic remission was first established on this baseline diet, prior to challenge with test substances encapsulated in clear gelatine. Following completion of the challenge protocol, long-term dietary modification based on individual oral provocation results was advised.

The initial clinical experience in 76 patients indicated that natural salicylates (aspirin) were one of the main groups of compounds which could precipitate recurrent idiopathic urticaria/angioedema, however, the literature revealed that published information about their presence in food was limited. Consequently, a systematic analysis of the total salicylate content of commonly eaten foods was undertaken using thin layer chromatography and high performance liquid chromatography, after which the elimination diet was modified and charts were constructed which could be used by salicylate-sensitive individuals to control the total daily dose of salicylate consumed.

It then became apparent that adverse reactions to food may cause not only symptoms involving the skin (recurrent idiopathic urticaria/angioedema), but also of the gastrointestinal tract, respiratory tract and/or central nervous system. Clinical observation suggested that in these patients a variety of other food additives and natural compounds might be implicated in provoking some of their symptoms. The challenge battery was therefore expanded and made double-blind to allow for the extensive and objective investigation of all patients presenting with more subjective symptoms (such as migraine, irritable bowel and neuropsychiatric symptoms). Over 3000 patients with varying manifestations of food intolerance have now been investigated. Susceptibility appears to be familial, more widespread than generally appreciated and there is strong circumstantial evidence to suggest that reactions are pharmacological in nature (rather than immunological). Reactions appear to be dose-related, and sensitive patients may exhibit withdrawal and supersensitivity, as well as tachyphylaxis and tolerance after reintroduction. Overall, natural salicylates are the single commonest substance to produce reactions when tested by double-blind oral challenge. Most patients are sensitive to multiple substances (between 2 and 10 commonly), and the effects can be additive.