title: Asthma and odors: the role of risk perception in asthma exacerbation.
abstract: OBJECTIVE
  Fragrances and strong odors have been characterized as putative triggers that may exacerbate asthma symptoms and many asthmatics readily avoid odors and fragranced products. However, the mechanism by which exposure to pure, non-irritating odorants can elicit an adverse reaction in asthmatic patients is still unclear and may involve both physiological and psychological processes. The aim of this study was to investigate how beliefs about an odor's relationship to asthmatic symptoms could affect the physiological and psychological responses of asthmatics.
  
  
  METHODS
  Asthmatics classified as 'moderate-persistent', according to NIH criteria, were exposed for 15 min to a fragrance which was described either as eliciting or alleviating asthma symptoms. During exposure, participants were asked to rate odor intensity, perceived irritation and subjective annoyance while physiological parameters such as electrocardiogram, respiratory rate, and end tidal carbon dioxide (etCO₂) were recorded. Before, immediately after, and at 2 and 24h post-exposure, participants were required to subjectively assess their asthma symptom status using a standardized questionnaire. We also measured asthma status at each of those time points using objective parameters of broncho-constriction (spirometry) and measures of airway inflammation (exhaled nitric oxide, FeNO).
  
  
  RESULTS
  Predictably, manipulations of perceived risk altered both the quality ratings of the fragrance as well as the reported levels of asthma symptoms. Perceived risk also modulated the inflammatory airway response.
  
  
  CONCLUSIONS
  Expectations elicited by smelling a perceived harmful odor may affect airway physiology and impact asthma exacerbations.
authors.affiliation: Monell Chemical Senses Center, USA.
authors.forename: Cristina
authors.initials: C
authors.lastname: Jaén
authors.affiliation: Monell Chemical Senses Center, USA. Electronic address: dalton@monell.org.
authors.forename: Pamela
authors.initials: P
authors.lastname: Dalton
mesh_terms: D000328:Adult; D001249:Asthma / Q000209:etiology* / Q000503:physiopathology* / Q000517:prevention & control; D002245:Carbon Dioxide / Q000032:analysis; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis; D009812:Odorants; D056152:Respiratory Rate; D018570:Risk Assessment; D012307:Risk Factors; D013147:Spirometry; D011795:Surveys and Questionnaires; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide; D009569:Nitric Oxide
keywords: Asthma; Exhaled nitric oxide; Fragrances; Nocebo effect; Odors; Risk perception