Despite aromatherapy's popularity, efficacy data are scant, and potential mechanisms
are controversial. This randomized controlled trial examined the psychological, autonomic,
endocrine, and immune consequences of one purported relaxant odor (lavender), one
stimulant odor (lemon), and a no-odor control (water), before and after a stressor
(cold pressor); 56 healthy men and women were exposed to each of the odors during
three separate visits. To assess the effects of expectancies, participants randomized
to the "blind" condition were given no information about the odors they would smell;
"primed" individuals were told what odors they would smell during the session, and
what changes to expect. Experimenters were blind. Self-report and unobtrusive mood
measures provided robust evidence that lemon oil reliably enhances positive mood compared
to water and lavender regardless of expectancies or previous use of aromatherapy.
Moreover, norepinephrine levels following the cold pressor remained elevated when
subjects smelled lemon, compared to water or lavender. DTH responses to Candida were
larger following inhalation of water than lemon or lavender. Odors did not reliably
alter IL-6 and IL-10 production, salivary cortisol, heart rate or blood pressure,
skin barrier repair following tape stripping, or pain ratings following the cold pressor.