During odor presentation, the subjects rated the odor's sensory properties, including intensity, irritancy, and annoyance. Measures of lung function and airway inflammation were collected before and immediately after exposure and again at two hours and 24 hours post-exposure.
Subjects' beliefs about the odor, specifically whether it was potentially harmful (asthma-triggering) or therapeutic, influenced both their psychological and physiological responses to odor exposure.
Individuals who were told that the odor was potentially harmful rated it as more irritating and annoying as compared to those who thought it might be therapeutic.
In addition, airway inflammation increased immediately following odor exposure in subjects who believed the odor might be harmful and remained elevated 24 hours later.
"Introducing a negative bias led to a rapid change in airway inflammation," said senior author Pamela Dalton, PhD, a cognitive psychologist at Monell. "What really surprised us was that this response lasted for over 24 hours. The increased inflammation during this period likely makes asthmatics more sensitive to other triggers."
There was no increase of inflammation when the odor was characterized as therapeutic, even in individuals who described themselves as sensitive to perfumes and other odors.
The findings suggest that some fragrance effects on asthma symptoms may be related to the expectation of harm as opposed to chemical properties of the odor.
"It's not just what you smell, but also what you think you smell," said Jan.
Looking forward, the researchers want to identify the biological mechanisms that connect expectations to airway inflammation. They also intend to explore whether a reverse phenomenon also exists. Dalton asks, "Ca
|Contact: Leslie Stein|
Monell Chemical Senses Center