These nerve cells regenerate every 30 to 40 days. Each specific aromatic molecule of essential oil reacts with specific nerve receptors, triggering an electrochemical impulse that is conducted directly into the brain. The aromas are transmitted to the limbic system, a part of the brain, which perceives and responds to memory, pleasure and emotions. Odor triggers the limbic system to release brain-enhancing neurochemicals. Enkephalin is a chemical that reduces pain and creates a feeling of wellness.
Endorphins also reduce pain and induce sexual feelings.
Serotonin helps relax and calm. Because the olfactory nerves are a direct extension of the brain's limbic system, recognition of smell is relayed immediately, recognition of taste, sound and touch is not transmitted immediately. The human brain's olfactory system contains thousands of memory packets, they are stored here along with the memory of pleasant scents and various odors. Each individual has their own perception of aroma, different preferences for various scents and specific memory's and responses associated with these scents. When you smell a scent that has been stored in this area of the brain it fires a memory packet and all of your memories associated with that scent come flooding back to you.