These molecules go up into your nose and get stuck to your olfactory membrane. The olfactory membrane contains olfactory receptors they have specialized nerve endings.
Millions of olfactory receptors work to identify millions of different scent molecules.
Once these nerves identify a particular scent molecule, they give a signal to your olfactory bulb, which signals your limbic and cortex system.

The cortex is where your brain process information. It is the centre of your perception, thoughts, creativity and language. Olfaction is the only one of your five senses that affects your cortex directly. Because of that, scents can recall such immediate reactions.
The other senses all need to pass through the thalamus to be processed.

Essential oil- aromatherapy affects your body's stress response and hormones.
Next, neurochemicals and hormones are released. Different neurochemicals and hormones create different reactions in your body. For example; if lavender relaxes you, as it does for many people, your brain will fill your body with relaxing hormones and produces soothing neurochemicals.

Take your self to the "Relaxation."
When your parasympathetic nervous system engages "Relaxation Mode" starts this is opposite of our "Fight or Flight " stress response.
When you're in the stress response; your body is flooded with cortisol and adrenaline, and everything goes into overdrive.
Cortisol hormone reduces the function of body systems that aren't essential in fight-or-flight situations — like the immune system, while adrenaline increases our heart rate and blood pressure.

The parasympathetic response works oppositely. It frees relaxing, feel-good hormones and allows your body to relax, rest, restore, and heal.
Aromatherapy can affect the immune system, also can help overall health. Aromatherapy can help to activate the parasympathetic response, but it also has a direct impact.

So how does your body consume and use essential oils?
When you inhale the essential oils (aromatherapy), the molecules are going to absorb into your body through your nasal passage-olfactory membrane- sinuses-trachea and lungs.
The therapeutic components are absorbed and ready to get right on your internal superhighway! These components have multiple effects on our body and many of which have been researched.

Imagine all the things you put your body that causes inflammation. Alcohol, trans fats, sugar, overdoing omega, even failing to floss can cause low-level chronic inflammation!
Now imagine accustoming/conditioning your body with an aromatherapy oil like lavender, which can gently but persistently reduce inflammation, while helping you relax and release stress.
Aromatherapy truly does affect your body in a holistic, comprehensive way. Your hormones, emotions, and healing responses are all set for the better!