The bronchial-provocation test (BPT) evaluates how sensitive your airways are to a particular substance. Health professionals use it to test for allergic asthma when a patient has no other symptoms. People who have suspected occupational asthma but don’t know the allergen causing it also receive this test for diagnosis. It is done after you take a small dose of methacholine, a drug that causes the airways to narrow in people with asthma. Then a spirometer is used to measure lung function and record changes.