In difficult cases, a positive, carefully controlled inhalation challenge test performed in the laboratory confirms the cause of the airway obstruction. Pulmonary function tests that show decreasing airflow during work are further evidence that occupational exposure is causative. Differentiation from idiopathic asthma is generally based on the pattern of symptoms and the relationship to exposure to allergens. If possible, a highly susceptible person should be removed from a setting known to produce asthmatic symptoms. If exposure continues, symptoms tend to persist.
Evidence suggests that some agent in the cotton bract leads to development of bronchoconstriction.
Prolonged exposure to cotton dust was once thought to lead to emphysema and irreversible obstruction, but these effects now seem unlikely in view of a series of postmortem studies that have shown some bronchitis but no increased prevalence of emphysema or destructive parenchymal changes. Chest tightness develops on the first day of work after a weekend or vacation. In many persons who complain of chest tightness, ventilatory capacity drops during the first work shift. However, with repeated, prolonged exposure over a period of years, chest tightness tends to return and persist through Tuesday and Wednesday, and occasionally to the end of the week or even permanently, as long as the person continues to work. Limited evidence suggests that occasionally, mild airway obstruction may develop and persist.