Effects of chiral fragrances on human autonomic nervous system parameters and self-evaluation

The effects of chiral fragrances (enantiomers of limonene and carvone) on t he human autonomic nervous system (ANS) and on self-evaluation were studied in 20 healthy volunteers. Each fragrance was administered to each subject by inhalation using an A-A-B design. Individuals were tested in four separa te sessions; in one session one fragrance was administered. ANS parameters recorded were skin temperature, skin conductance, breathing rate, pulse rat e, blood oxygen saturation and systolic as well as diastolic blood pressure . Subjective experience was assessed in terms of mood, calmness and alertne ss on visual analog scales. In addition, fragrances were rated in terms of pleasantness, intensity and stimulating property. Inhalation of (+)-limonen e led to increased systolic blood pressure, subjective alertness and restle ssness. Inhalation of (-)-limonene caused an increase in systolic blood pre ssure but had no effects on psychological parameters. Inhalation of (-)-car vone caused increases in pulse rate, diastolic blood pressure and subjectiv e restlessness. After inhalation of (+)-carvone increased levels of systoli c as well as diastolic blood pressure were observed. Correlational analyses revealed that changes in both ANS parameters and self-evaluation were in p art related to subjective evaluation of the odor and suggest that both phar macological and psychological mechanisms are involved in the observed effec ts. In conclusion, the present study indicates that: (i) prolonged inhalati on of fragrances influences ANS parameters as well as mental and emotional conditions; (ii) effects of fragrances are in part based on subjective eval uation of odor; (iii) chirality of odor molecules seems to be a central fac tor with respect to the biological activity of fragrances.