The sense of smell (olfaction) was one of the earliest senses to arise in evolution and is well developed in animals. In humans and animals, olfaction evokes emotional reactions that result in strong behavior changes. The limbic system is where our memories, instincts, and vital functions are controlled and processed.
When an essential oil is inhaled, the odor molecules travel up your nose where they are trapped by olfactory membranes. They are then carried to the limbic system where they pass between the major glands in the brain.
Smell is the only sense that goes directly to the limbic system,
bypassing the cerebral cortex, (our intellectual part of the brain).
The other senses of sight and hearing must register with the cortex before entering other parts of the