Indian Journal of Dermatology, Venereology and Leprology Medknow Publications on behalf of The Indian Association of Dermatologists, Venereologists and Leprologists (IADVL) ISSN: 0378-6323 EISSN: 0973-3922 Vol. 71, Num. 3, 2005, pp. 211-212

Indian Journal of Dermatology, Venereology and Leprology, Vol. 71, No. 3, May-June, 2005, pp. 211-212

Letter To Editor

Wheat induced urticaria?

Ramam M.

Department of Dermatology and Venereology, All India Institute of Medical Sciences, New Delhi

Correspondence Address: Department of Dermatology and Venereology, All India Institute of Medical Sciences, New Delhi - 110029, mramam@hotmail.com

Code Number: 05072

Sir,

In a recent report, Uppal and Srinivas[1] described a patient who had chronic urticaria for 8 years. The patient believed her urticaria was due to Samba Rava (coarsely ground whole kernel of wheat). Skin prick tests were negative with whole wheat and wheat antigens in a commercial food series but were positive with raw wheat components including Samba Rava. Oral challenge with Samba Rava led to urticaria in half an hour. The authors concluded that the patient had wheat induced urticaria.

This report raises interesting and important issues related to food-induced urticaria. Patients looking for a cause for their urticaria often blame foods and drugs. In North India, the foods commonly implicated are brinjal, rice, curd, sour foods and non-vegetarian foods. In our experience, there is little correlation between the pattern of urticaria and the foods implicated by the patient. For example, a patient who has urticaria every day may implicate a food that is eaten only once or twice a month. Also, in most instances, stopping the incriminated food does not lead to significant remission and urticarial wheals continue to appear (though it is quite common for patients to state that the urticaria is worse on the day they take the suspected food). Far less commonly, the patient may correctly identify a food as the cause of his urticaria. In such cases, urticaria occurs every time there is exposure to the food and does not occur when the food is not taken. Apart from clinical experience, population studies have demonstrated that a perception of food hypersensitivity is much commoner than true hypersensitivity.[2],[3] These studies found that the proportion of people in the general population who complained of food intolerance was 20-34% while the prevalence of food hypersensitivity confirmed by double blind food challenge was merely 1.4-3.7%.

The second point of interest is the reliability and interpretation of prick test results in food urticaria. It is well known that false positive results are common with skin prick tests with foods.[4] It is for this reason that patients who undergo prick tests often receive a long list of forbidden foods leading to unnecessary and potentially harmful dietary restrictions. When testing with non-standard antigens such as raw foods, it is important to also test the antigens in controls to rule out false positive reactions. In the present case, knowing the frequency of positive prick tests with Mav, Rava and Samba Rava in patients with urticaria not due to wheat would help establish the specificity of the test.

Challenge testing is a reliable diagnostic procedure in hypersensitivity disorders. Double blind placebo-controlled food challenges are considered the "gold standard" for diagnosing food allergy.[5] However, an open challenge test also provides good evidence of causation provided it is supervised and the development of urticaria is confirmed by the dermatologist. The challenge must obviously be carried out only after the patient is free of urticaria since otherwise a spontaneously occurring episode may be mistaken for a positive reaction.

Finally, the real test of any method to establish the etiology of urticaria is the difference that it makes to the patient′s disease. Except for inadvertent intake, avoidance of the implicated food should lead to cessation of urticaria.

In order to be able to evaluate the role of wheat in causing urticaria in the patient reported by Uppal and Srinivas, it would be helpful to know the frequency with which urticaria occurred, the frequency with which Samba Rava and other wheat products were eaten by the patient, and the course of urticaria after the patient stopped eating Samba Rava.

REFERENCES

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