Smell the stress: Subjective ratings of body odors reliably indicate stress levels

Background: Chemosensory signals like body odor carry information about the emotional state of individuals like fear or stress. Analysis of sweat odor could therefore deliver an easy option of assessing stress. Our aim was to examine if subjective odor ratings can reliably and validly capture characteristics of sweat odor. For this we presented odor samples of stressed individuals to naïve participants who rated these concerning their intensity, valence, and stress. Furthermore, we compared odor rating results to well-studied physiological markers of stress that we obtained from the odor donors during the stress task.

Method: Odor donors were 30 men and 30 women who performed a standardized protocol to induce social stress while wearing axillary pads under each armpit. Additionally, we measured   cortisol in saliva, adrenaline in blood and recorded participants’ heart rate. For odor ratings, we recruited an independent sample of 40 individuals. Participants rated the odor samples using visual analog scales.

Results: Intraclass correlations revealed a fair level of clinical significance for intensity and valence of sweat odors. Additionally, retest reliability was moderate for these two odor qualities. Ratings of stress also showed a moderate retest reliability, but the intraclass correlation was on a poor level. In further analyses we found significant relationships between all three qualities. Correlations between subjective ratings of body odors and physiological stress markers of odor donors were not significant.

Discussion: Our data show that subjective ratings of body odor qualities, in particular intensity and valence are reliable. Further research on validity is needed.