Occupational Asthma (OA) is a disease characterized by variable airway limitation and airway hyper responsiveness due to causes and conditions in a working environment and not to stimuli encountered in a working place. Asthma is now the most common occupational respiratory aliment in developed countries.

OA in the absence of latency period is referred to irritant induced asthma or reactive airway dysfunction syndrome (RADS). Precise statistics regarding the overall prevalence of OA are not currently available , but it is estimated that 2% to 15% of all cases of asthma may be occupational in origin . Prevalence figures of OA vary due to factors such as : host susceptibility , the level, type and quality of exposure . There are now more than 300 agent known to induce asthma and this list will continue to grow as industrial technology becomes more sophisticated and additional chemical are introduced into the workplace. All of these compounds are inhaled . Two major groups of agents responsible for OA: 1-High molecular  weight  heterologous  proteins of animals,  plants and microbes,  e.g ; cereal proteins or insect contaminants contained  in flour ( bakers , millers ), enzymes ( in plastic and laundry detergents). 2-low molecular weight chemicals (>3 Kd), e.g; isocyanides (plastic , painting), anhydrides (plastics , epoxy resins). Diagnosis relies on a detailed and thorough occupational history, quantitative exposure measurement ,  antibody testing (Skin Prick Test, RAST or ELIZA), PFTs and provocative tests .Avoidance is the best rational treatment.