Aromatherapy is actually a large field. The effects of natural ethereal oils such as lemon are being used in Japan to better the concentration of the employees, and the employers report significant improvement.
Robert Tisserand, a famous therapist from England describes, that synthetic
substances are being researched by the Army.
(Synthetic aromas, which don't exist in nature cause fear and the wish to escape)
He was allowed to smell a substance in high dilution, created for military purposes, and felt very unpleasant, while others had to leave the building on the spot.
"Dangerous" smells, such as smoke and of rotting bodies alert us and can keep us safe, (if we stay away)
Scents and smells affect our limbic system and can cause the excretion of neurochemical substances, such as encephalines, (spelling?) endorphines, serotonine and noradrenaline.
The effect of natural
ethereal oils can be used to relax and influence disharmony in mind and body. (So perhaps make your wife aware you only want natural aromas)
Lavender, for instance, is relaxing, it is said to balance blood pressure and to enhance sleep. It also helps to keep insects away.
Here some oils and their effects:Refreshing; enhancing concentration:
Bergamotte, lemon, lime, grapefruit, lemongrass, rosemary, basil, peppermint, stone pine and juniperRelaxing, or for the evening:
Orange, cinnamon, honey, vanille, melissa, mimosa , rose, lavender, neroli, (orange blossoms) Petit grain, myrtle, cedar.
Now to sandal wood.
As Peter rightly said, it is a very special scent.
The description says:
Sandalwood has a very deep, slow vibration, it is harmonizing, relaxing and calming.
It is slow and powerful like an Indian elephant.
If one is aggressive and stressed, it is time to benefit from sandalwood.
In Yoga, Sandalwood is associated with both the lowest root chakra,(sexual power), and the highest chakra, (wisdom and enlightenment).
It is described as the oil of the "subtle body", (highest enlightenment body) and so as the aura of a human being which transcended all delusions.
Hope all this was useful, and if you got any more questions, feel free to ask!
And as Ben rightly said, they can support us, (why not) but we have to do the rest.