The vehicle tray revisited: the use of the vehicle tray in assessing allergic contact dermatitis by a 24-hour application method.

Over 700 patients were screened by patch testing for sensitivity to the components of a vehicle tray from July 1974 through June 1976 at the Mayo Clinic. A modified version of the vehicle tray originally suggested by Fisher et al. (1971) was used, containing 14 substances commonly found in vehicles. Patches were applied for 24 rather than the usual 48 hours. Our percentage of reactivity compares favorably with the 48-h application method, thus demonstrating the efficacy of this time-saving technique. The method and usefulness of determining a percentage of irritancy are discussed. This was found to be a valuable tool in assessing false-positive reactions among our percentage of reactivity. Four irritants were demonstrated: phenylmercuric acetate (0.05% pet.), sodium lauryl sulfate (1% aq), thimerosal (0.1% aq) and hexachlorophene (1% pet.).