Patch Testing With a Patient’s Own Materials Handled at Work

Almost 20 million individual chemical substances have been identified according to the Registry of the Chemical Abstract Service (CAS) numbers and, annually, 1 million substances enter the registry. Most of the registered substances are not significant in practice. The number, type and quantities of chemicals used vary, depending on the national economy, level of industrialization, and the extent of agriculture in the country. The European Inventory of Existing Commercial Chemical Substances (EINECS), established in the beginning of the 1980s, contains about 100,000 chemicals supplied by their importers or manufacturers. Workers are constantly exposed to new chemicals as, every year, thousands of new molecules are synthesized and hundreds of chemicals and formulations come on the market, older ones being replaced by better new alternatives. Also the variety of chemical substances hazardous to the skin is enormous; for example, De Groot (1994) listed about 3700 contact allergens.