Scientists in the US have been conducting research that suggests some individuals with allergic reactions to smell may be caused by what they think they smell, rather than the actual scent.
A research team at the Monelll Chemical Senses Center , in Philadelphia, Pennsylvania, says its research reveals that simply believing an odor is harmful can increase airway inflammation in asthmatics for up to 24 hours after exposure.
"Asthmatics often are anxious about scents and fragrances. When we expect that an odor is harmful, our bodies react as if that odor is indeed harmful," said study lead author Cristina Jaén, PhD, a Monell physiologist.
"Both patients and care providers need to understand how expectations about odors can influence symptoms of the disease."
Is fragrance allergy formed from bias?
Asthma is widespread in the US, thought to affect upwards of 25 million individuals, and with an increased number of reports citing allergic reactions that include asthma from cosmetic and personal care fragrances as well as perfumes, the study is particularly pertinent.
Triggers for asthma include pollen, dust, irritating chemicals and allergens and strong asthmatic reactions can in some cases lead to death.
Many health organizations list scents and fragrances as a trigger for asthma, which can lead to patient anxiety when they are exposed to these odors.
Individuals who were pre-warned of allergy, reacted
The study, which was published in the peer-reviewed publication Journal of Psychosomatic Research, analyzed 17 individuals with moderate asthma, who were all exposed for 15 minutes to the rose-smelling odor phenylethyl alcohol (PEA), which is commonly associated as being a physiological irritant.
Of the study group, eight individuals were told that the odor had potential therapeutic qualities, while the remaining nine were told that it could cause mild respiratory problems.
All 17 individuals were asked to assess the odor for sensory properties, including intensity, irritancy and annoyance, and where in turn also assessed for airway inflammation, both before and after exposure.
Reaction appeared to be predetermined
According to the researchers, those individuals that were told the chemical was a potential irritant reported increased airway inflammation and also rated as being more harmful, compared to the group who were told it had therapeutic properties.
"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."
The findings underline a clear correlation to a psychosomatic response to fragrance allergy due to expectations, rather than an actual physiological reaction.
Taking the research forward, the team at Monell now want to identify the biological mechanisms that connect expectations to airway inflammation, as well as exploring if a reverse phenomenon exists.