[Role of sodium nitrite in histamine urticaria of dietary origin]

Although genuine gastro-intestinal allergy is sought as the cause of chronic urticaria or repeated vaso-motor headaches, a non-allergic intolerance of one or more ingested substances, additives to foodstuffs (colourants and conserving agents) are likely to be implicated. Dietary histories from such patients often reveal heavy consumption of charcuterie. Oral provocation tests, performed using additives and placebo, can reproduce symptoms reliably. The substance most frequently incriminated is sodium nitrite (E 250): out of 76 tests, 4 were positive and 4 doubtful. In these cases complete avoidance of E 250 led to significant improvement or cure. We discuss various hypotheses on the harmful effects of sodium nitrite, such as denaturation of histamine-binding SH-group rich mucoproteins, direct toxicity on microvilli or inhibition of intestinal histaminase.