Fragrances are not ambiguous, but have effects. In this report, we will focus on the animal experiments that our research group has conducted. In the course of our research, we have come to understand not only the positive aspects of fragrances, namely their effectiveness, but also the negative aspects, namely their risks. In order to actively utilize fragrances in clinical practice, it is necessary to be aware of not only the positive aspects but also the negative ones. The current situation is that there are too many fragrances around us. We are now at a stage where we need to make more effective use of fragrances, taking into account their risks.

Since ancient times, we have examined the anxiolytic effects of odorous compounds derived from plant extracts. Nowadays, the effects are introduced for the treatment of folk remedy. However, the neuronal mechanisms underlying the odor-induced anxiolytic effects has not fully addressed yet. In this review, the anxiolytic effects of odor of linalool (one of the major odorous compounds in lavender extract) which is triggered by olfactory input via endogenous benzodiazepine-like transmitter in the brain.

Most modern people have complained chronic sleep loss and decreased sleep quality. Sleep problems lead to immunological dysfunction, cognitive impairment and increased risk of neuropsychiatric diseases including dementia and depression. Because it is difficult to get enough sleep time for modern people who work around-the-clock, sleep issues remain unsolved. Aromatherapy, a complementary and alternative medicine, has been proved to improve sleep quality. The present review introduces and summarizes current findings along with our research on the beneficial effects of aromatherapy using natural essential oils on sleep loss-induced hippocampal dysfunction and spontaneous sleep in animals.

Aromas which have sedative effects are expected, based on prior aroma research, to enhance sleep quality. Expression of the sedative effect is reported to be due to suppression of the parasympathetic nervous system activity by black tea aroma. In this study we analysed the effects of tea aroma on sleep in 20 healthy females with high levels of self-perceived stress and sleep dissatisfaction over a 14-day test period. Psychological effects were observed as a reduction in perceived stress, as well as improved satisfaction with sleep quality, ease of sleep onset and sleep maintenance; while physiological data showed reduced sleep latency and bed out time, increased total sleep time, and a significant increase in sleep efficiency, suggesting black tea aroma has an ameliorating effect on sleep quality.

α-Pinene was introduced into hydrolysable polymers by melt blending method. α-Pinene was released over 10 to 20 days by hydrolysis of polymers in acidic aqueous solution. Release rate of α-pinene increased with an increase in hydrophilicity of the polymer; that is, hydrophilicity accounts for its enhanced degradability. However, mechanical strength of the polymers decreased up to 20 to 30 % of their initial strength by incorporating of α-pinene into polymers.