One hundred patients suspected of having allergic eczematous contact dermatitis due to topically administered medications were patch tested with a "vehicle tray" composed of 15 substances commonly found in vehicles of current preparations. Positive tests were obtained in 30 of 100 patients. There were 18 reactions to ethylenediamine; 6 to lanolin; 3 to parabens; 2 each to phenylmercuric acetate, thimerosal, dichlorophene, propylene glycol monostearate, and triethanolamine; 1 to sorbic acid for a total of 40 positive reactions. Vehicles play a significant role in producing sensitization and allergic contact dermatitis. The importance of testing with a standard concentration of each ingredient in preference to the total formulation is shown by the sizable incidence of false-negative reactions with the total formulation.
Fisher AA, Pascher F, Kanof NB. Allergic Contact Dermatitis Due to Ingredients of VehiclesA "Vehicle Tray" for Patch Testing. Arch Dermatol. 1971;104(3):286-290. doi:10.1001/archderm.1971.04000210060011