Hyposensitization to urushiol among Japanese lacquer craftsmen: results of patch tests on students learning the art of lacquerware.

8 subjects learning the art of lacquerware were patch tested to urushiol before and after contact with lacquer, in order to document whether hyposensitization to urushiol occurred among Japanese lacquer craftsmen. Simultaneously, we performed patch tests on 2 urushiol-sensitized controls who had no contact with lacquer during the investigation. Lacquer is made from the sap of the Japanese lacquer tree and raw lacquer is composed of 60-65% urushiol and its oligomer. 5 of the 8 subjects showed positive reactions to urushiol 1 month after their first contact. They became negative or less positive after prolonged (9 or 10 months) exposure to lacquer. As reactions to urushiol decreased, dermatitis became less severe. Controls showed consistently high reactions. However, 1 subject showed persistently strong reactions to urushiol. Unlike the other 7 subjects, he was previously sensitized to urushiol before the first contact with lacquer. The remaining 2 subjects showed no reaction throughout our investigation. These results strongly suggest that hyposensitization to urushiol does occur among Japanese lacquer craftsmen.