At this stage, personal factors for susceptibility (genetic factors, propensity for allergies or unusually irritable bronchial tubes, smoking, various psychosocial factors, etc.) may increase the risk of developing asthma or sensitization to an agent in the workplace.
External factors may also increase the worker's risk of becoming allergic, such as factors in nature (some agents are more allergy-inducing than others), the concentration and length of exposure to the agent in the workplace, and the occurrence of viral infections or exposure to pollutants.
Once an allergy has been acquired to the agent in the workplace, the worker's propensity for developing bronchial hyperexcitability may increase the risk of developing asthma. Before asthma develops, there is probably an intermediate state of inflammation of the mucous membranes in the upper respiratory tract and the bronchial tubes.
Once symptoms of asthma develop, it is important to make a diligent and objective diagnosis. A worker who remains exposed and symptomatic for too long will present with more severe asthma and run a greater risk of experiencing permanent after-effects that will manifest as chronic asthmatic symptomatology. The diagnosis of occupational asthma should not be based solely on the clinical history, however. The fact that asthmatic symptoms develop or grow worse at work does not necessarily mean that the asthma is caused by the workplace. Objective tests have been suggested for effective diagnosis of the disease.
Once a diagnosis of occupational asthma has been made, it is important for the worker not to have any further exposure to the agent that is causing his or her asthma, and anti-inflammatory therapy should be offered to maximize the worker's chances of recovery. A social rehabilitation program should also be offered so that the worker is able to enjoy his or her work again.