1. Torri and the method of cutaneous potentials (P.C)
The cutaneous potentials are classically used in human physiology to measure the cutaneous perspiration, reflection of the autonomous nervous system functioning and directly linked to the emotional state of the subject: -40 mV at waking, -60 mV under excitation and 0mV during sleep time.
These measures used on a very large number of volunteers enabled him to test most of the important odors and to classify them according to their sedative or stimulating properties.
According to this method, camomilla was classified among the most sedative and jasmine among the most stimulating ones.
The German team of W. Steiner on the 12 most demonstrative odors has confirmed this study.

2. Torri and Kubota and the measurement of the "contingent negative variation"
This technique detects by the means of electrodes hung on the scalp certain modifications of the electrical activity of the brain giving the level of alertness, vigilance, and emotion of the subject. Torri and Kubota thus studied the physiological effects of 18 odors on male and female volunteers and reached results comparable to the previous ones. The oil of rose was the only one to have an unexpected effect: generally considered as sedative, this oil made the VNC grow.

3. Konishi and the peripheric blood pression
The measurement of peripheric blood pressure variations is an excellent witness to the activity of the sympathetic nervous system, which is intensified in situation of stress. Konishi thus managed to test a great number of odors according to their ability to reduce or to intensify the adrenergical effects and to attain a general classification of the relaxing and the stimulating odors.

4. Oguri and the variations of the cardiac frequency
The cardiac rhythm reflects faithfully the state of tension, emotion or relaxation of the subject.
Using this technique, Oguri was able to separate clearly the stimulating scents from the sedative scents.
With the same protocol, Kikuchi showed that the essence of rose maintained the cardiac excitability whereas the essence of lemon reduced it.

5. Steiner and Miyazaki: variations in pupil dilation
Steiner had already shown in 1977 that most of the scents used in aromatheraphy or in perfume stores, had an emotional charge responsible for a mydriase or a pupil dilatation.
Miyasaki, 14 years later, refined this experiment by using it during a cognitive test in which the subjects, in situation of stress, were already in a mydriase state.
He thus was able to observe that some scents, sympathomimetical, would accentuate this mydriase whereas some others, parasympato-mimetic, such as the essential oil of orange, would reduce it.

6. General synthesis of Sugano at the 22nd Japanese symposium on Taste and Smell
The teams of Lorig in Washington, Van Troller in Warwick (U.K.), and Kobl in Erlangen (F.R.G.) are distinguished for their pioneering work on the effects of odor in the mood, the emotions, and the effects, made objective through EEG on the electrical waves of the brain.

However, the Japanese resumption of these studies again brought them to a considerably deeper level, using the most sophisticated techniques of brain investigation.
Regrouping the electrical wave study of the brain (waves of concentration, of vigilance and of emotion, and waves of rest), the potentials evacuated, the VNC and even the measure of the brain flux which nowadays is the advanced tool to "read the Brain,". Sugano concludes that all these methods converge to oppose and classify the 50 most usual scents into sedative scents and stimulating scents. He thus resumed, with the most advanced experimental verifications, the first conclusions of Torri:

1. The most sedative of these scents, such as lavender, orange, rose, linalool, isogenol, santal wood, etc., produce circulatory, electrical, CNV, etc. brain reaction similar to administering tranquilizers.

2. The most stimulating ones, such as jasmine oil, produce an effect similar to administrating caffeine

Withdrawal from the chemical medication of insomnia (tranquilizers and hypnotiques) by the use of an environmental sedative odor. M. Hardy, D. Kirk Smith, D.D. Strech. (Lancet 10/9/95 issue)

Following the Japanese trail, a medical team from the Ulster and Leicester University led by Hardy, Kirk Smith and Strech worked in the psycho-geriatric environment on insomniac patients treated with tranquilizers and hypnotics on a long- term basis (from 7 months to 3 years).


Their study was composed of the analysis of three periods:
1) Measure of the time of diurnal sleep under hypnotics for 2 weeks.
2) Measure of the time of sleep after a 2 week long withdrawal.
3) Measure of the time of sleep under a sedative odors ambiance (lavender components).

 

At the end of their study, these authors conclude:

 

* The results suggest that the duration of sleep was significantly reduced after withdrawal of the hypnotics, but that the duration of the sleep was back to the same level with the ambient scent as under medication
* These patients also reported they have obtained a more restful and recuperative sleep
* They conclude: The study suggests that the essential lavender components maybe used as a temporary replacement of the long-term medication of insomnia.