Once a person has developed hypersensitivity to a material or organism, he or she may experience symptoms the next time exposure occurs.
These symptoms usually develop in four to eight hours and include:
- Shortness of breath
The symptoms usually clear up in a day or two if there is no more exposure to the reaction-causing material. Complete recovery, however, may take weeks.
In one form of hypersensitivity pneumonitis, a cough and shortness of breath may take days or weeks to develop and be so severe that the person needs to be hospitalized. If a person is repeatedly in contact with an allergen over months or years, the lungs may become scarred (fibrosis). Symptoms in this case may include shortness of breath during exercise, coughing up of sputum, tiredness and a gradual weight loss. Eventually, respiratory failure can occur.
Causes and Risk Factors
Many types of dust, organisms or chemicals can cause allergic reactions in the lungs, including:
- Heat-loving bacteria in moldy hay
- Contamination in humidifiers or air conditions (especially large systems in office buildings)
- Chemicals, such as urethanes (isocyanates)
- Wood dust
- Droppings from poultry or other birds.
- Chemicals used in making polyrethane foam, molding, insulation, synthetic rubber and packaging materials.
- Materials found in certain types of farming or food production or processing, including mushroom compost, moldy cork, infected maple bark, moldy barley or malt, cheese mold, sugar cane, unroasted coffee beans or weevil-infested wheat flour