Patch test allergens currently are classified as drugs in some countries, whereas in other countries they are evaluated on a physician- or patient-named basis. The European Economic Community legislature passed guidelines for allergens that still have to be adopted by the member nations. In the United States, the regulations for patch test allergens by far exceed these guidelines. On acceptance, European manufacturers of patch test allergens will have to provide the same information for every single allergen as they do for a drug, eg, toxicity, pharmacodynamics, clinical efficacy, and stability data. This overview will deal with the problems that have to be solved in these respects. Most patch test allergens are chemicals used in different branches of industry. They never have been considered a drug and as a consequence they have not been developed or tested under these circumstances. Nevertheless, the safety of the patients and the validity of the test results have to be the main emphases of both manufacturers and dermatologists. Taking this into consideration, the quality of any material used for patch testing, the standardization of production procedures, and the stability control of the final product will be discussed in relation to legislation demands.