Occupational allergies are among the most common recorded occupational diseases. 
The skin and the upper and lower respiratory tract are the classical 
manifestation organs. More than 400 occupational agents are currently documented 
as being potential "respiratory sensitizers" and new reported causative agents 
are reported each year. These agents may induce occupational rhinitis (OR) or 
occupational asthma (OA) and can be divided into high-molecular weight (HMW) and 
low-molecular weight (LMW) agents. The most common occupational HMW agents are 
(glycol)proteins found in flour and grains, enzymes, laboratory animals, fish 
and seafood, molds, and Hevea brasiliensis latex. Typical LMW substances are 
isocyanates, metals, quaternary ammonium persulfate, acid anhydrides, and 
cleaning products/disinfectants. Diagnosis of occupational respiratory allergy 
is made by a combination of medical history, physical examination, positive 
methacholine challenge result or bronchodilator responsiveness, determination of 
IgE-mediated sensitization, and specific inhalation challenge tests as the gold 
standard. Accurate diagnosis of asthma is the first step to managing OA as shown 
above. Removal from the causative agent is of central importance for the 
management of OA. The best strategy to avoid OA is primary prevention, ideally 
by avoiding the use of and exposure to the sensitizer or substituting safer 
substances for these agents.