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Perceived harmful odor increased airway inflammation in patients with asthma

Patients with asthma who perceived an exposure risk toward a benign nonirritant odorant exhibited increased airway inflammation up to 24 hours after exposure to the odor in a recent study.

“Asthmatics often are anxious about scents and fragrances,” researcher Cristina Jaén, PhD, a physiologist at the Monell Chemical Senses Center, Philadelphia, said in a press release. “When we expect that an odor is harmful, our bodies react as if that odor is indeed harmful. Both patients and care providers need to understand how expectations about odors can influence symptoms of the disease.”

Jaén and Pamela Dalton, PhD, MPH, a cognitive psychologist at Monell, studied 17 patients with asthma. Eleven were classified as having mild asthma (FEV₁ greater than 80%), and six had severe asthma (FEV₁ lower than 60%). All patients were exposed to 15 minutes of a phenylethyl alcohol fragrance, described as a “rose odor,” normally considered pleasant.

Nine patients (age range, 18 to 55 years; four women) were assigned to the “therapeutic” group, in which the fragrance was described as a healthy condition, while eight others (age range, 21 to 55 years; four women) were assigned to the “asthmogenic” group, in which the fragrance was described as harmful.

Using questionnaires, participants rated odor intensity, perceived irritation and subjective annoyance, and asthma symptom status before, immediately after and at 2 and 24 hours post-exposure. Bronchoconstriction was measured through spirometry, and airway inflammation was assessed by fraction of exhaled nitric oxide at the same time points.

Participants in the asthmogenic group rated the odorant as more irritating and annoying than those who in the therapeutic cohort. The asthmogenic group also exhibited increased airway inflammation for up to 24 hours after exposure.

“Introducing a negative bias [also] led to a rapid change in airway inflammation,” Dalton said in the release. “What really surprised us was that this response lasted more than 24 hours. The increased inflammation during this period likely makes asthmatics more sensitive to other triggers.”

Disclosure: The researchers report no relevant financial disclosures.