Definition: A test for hyper-reactivity of the smooth muscles of the lungs, often used to determine the presence or absence of asthma. Lung function drops as a result of inhaling the chemical methacholine, which constricts the muscles around the airways in the lungs. False-positive results are common and often caused by cigarette smoking, viral infections and presence of allergies. False-negative results are rare if the test is performed correctly, so a negative test can be used to reliably rule out the presence of asthma.
Also Known As: histamine challenge
