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August 12, 2013
Food Intolerance and Chronic Urticaria
I am an allergist in Australia where low food-chemical diets are often tried in chronic urticaria. Many academic publications from the USA state that such diets have a limited role in this condition. These diets are often used in Europe, where they are often called 'pseudo-allergen diets'. Are there any RCT studies on this intervention? Can you advise on this diet's role in chronic urticaria?
At first a very important misunderstanding is the term in the question low food chemical diet. The data in the literature and also in the reference in the guidelines is on so called pseudoallergenfree-diet (synonyms for the term of a pseudoallergen reaction are non IgE-mediated hypersensitivity reaction. Pseudoallergen is the more frequently used term in Europe especially as in the official terminology there is no word for the causative agent the “pseudoallergen”.
The important point why it is not called low food chemical diet is that it is known that not only chemical food additives as believed earlier are the cause. More important, naturally occurring components in food like salicylates but very important also naturally occurring aromatic compounds especially in vegetables are important. There is no dispute that academic publications from the USA state that such diets have limited role in the condition of chronic urticaria but as in many other areas of medicine it is extremely important to exactly look at the subset of the population.
The currently suggested diet (see related PDF) has been evaluated and controlled in trials in different European countries by different groups have shown very similar results. In general the diet is especially helpful in those patients with chronic urticaria with daily or almost daily whealing and the history of intolerance (synonym: pseudoallergy) to Aspirin. The pathology is not clear but it has been shown that those patients with chronic urticaria who have a disturbed gastric permeability are those responding to diet and that adhering to the diet for three to four weeks can restore gastric permeability to normal levels.
Using the diet in diagnosis and treatment of course is only useful if the patient is willing to adhere in the time of diagnosis for at least three weeks. Afterwards the diet can be gradually expanded if helpful.
Charité - Universitätsmedizin Berlin – Germany
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