Criteria for prick test using soy sauce

AbstractBackground  We previously reported four cases of soy sauce allergy and noted that new criteria are necessary for the prick test. Soy sauce contains histamine and often causes false‐positive reactions in the skin tests. It is important to discuss how to interpret the results of prick tests.Materials and methods  Eight female patients with soy sauce allergy and four female volunteers as controls were given the prick test using 15 sauces and were evaluated according to nine criteria. The volume of histamine in 15 sauces was determined by high‐performance liquid chromatography.Results  The conventional criteria resulted in nine different reactions. Some of the control subjects showed false‐positive reactions according to the conventional criteria. Histamine was detected in 11 sauces and was not detected in four sauces. The positive ratios of these four sauces were low; there were no positive reactions in controls according to the new criteria. Regardless of patients or controls, the positive ratio evaluated using the conventional criteria was higher than that evaluated using the new criteria in the sauces containing histamine.Discussion  It is difficult to evaluate the results of the prick test using soy sauce with the conventional criteria because the results were different depending on each criterion. Our new criteria are more suitable for evaluating the results of the prick test using soy sauce than the conventional criteria, and they could decrease the number of false‐positive reactions. Common diagnostic criteria are needed for prick testing using pseudoallergens.