Patch test materials in petrolatum, from 3 different manufacturers and 14 different types were evaluated by gross and microscopic examination. The allergens were noted to be suspended as particles or droplets in the vehicle. Obvious variations in both size and structure of the included allergen were found with the same chemicals but of different manufacture. Several materials do not meet the pharmaceutical standards which should be requested regarding stability, particle size and packing. A more detailed declaration is proposed.