The use of immunoassays has facilitated the measurement of high molecular weight sensitizers, usually protein molecules, in the picogram and nanogram per cubic meter range. This facilitated the evaluation of exposure response relationships for bakery workers, exposed to wheat allergens and fungal alpha-amylase and other groups exposed to other allergens such as laboratory animal workers. The application for the standard setting is still limited and requires rigorous standardization, but can be expected in the near future.