Nitric oxide levels did not change at all among the group who thought the smell was therapeutic, but those who believed it to be asthmogenic had an immediate rise in exhaled nitric oxide that continued to climb. Just after exposure, levels had risen by 36 percent; two hours later they were 56 percent higher, and the next day levels were elevated by 65 percent.

the findings suggest that certain activities, odors and images may elicit a stress response that causes physiological symptoms in asthma patients