Perioral contact urticaria from sorbic acid and benzoic acid in a salad dressing.

Contact urticaria was observed in a kindergarten in 18 of 20 children following the intake and accidental perioral application of a mayonnaise salad cream. In healthy adult controls, stinging tests and closed 20 minute patch test with the salad dressing were positive in 9 out of 12 and 4 out of 10 cases respectively. Twenty minute patch tests with the different components of the salad dressing were positive only so sorbic acid (SA) and benzoic acid (BA). Urticaria was provoked by inunction of the salad dressing periorally in two healthy boys. Serial 20 minute closed patch testing with varying concentrations of SA in 91 patients and BA in 41 patients gave almost identical results: positive reactions in two thirds of the patients with the highest concentrations. The response was only partially blocked by antihistamine applied locally before testing. Non-immunologic mechanisms are probably responsible for the transient reaction, and no restriction in the extensive use of SA or BA as preservatives in food should be considered.