A lot of people think of aromatherapy as a slightly "woowoo" hippie thing that doesn't pack a punch, but let me tell you that I've got a deep hole in my computer case. I got it because I placed a bottle of Rose Geranium essential oil on it and it must have leaked a drop or two - and burned straight through the space age plastic!
Apart from the fact that aromatherapy essential oils are madly concentrated - over a million flowers go into a single bottle of Jasmine, for example! - it is their intensive effects on the olfactory system, human smell, that makes them such a perfect choice for stress relieving.
Smell is the only one of our major senses that is not routed through the neo cortex and goes straight into the "reptilian brain" - the oldest parts of our brain, and the ones that have a lot to do with how we experience especially danger and stress.