Aromatherapy works by stimulating the nervous system through the inhalation of essential oils (therapeutic oils extracted from various aromatic plants) , which can then trigger a chain reaction of signals to the brain and affect the body's chemistry.

The scent molecules of essential oils stimulate olfactory receptors in the nose, sending messages to the brain's limbic system, the emotional center, and hypothalamus, influencing mood, memory, and hormone release.

Aromatherapy work on the body through 3 different pathways - the cutaneous pathway (through the skin),
the respiratory pathway (through the membrane of lungs), the olfactory pathway (through the neuro-endocrine system)

Yes, aromatherapy oils, also known as essential oils, can be used on the skin, but they must be diluted with a carrier oil before application.

It's necessary to dilute the essential oils before using. Depending on your skin sensitivity and the strength of the oil, pure, undiluted essential oils can cause skin irritation, redness, or allergic reactions.

Here's why dilution is important and how you do it:

• High Concentration: Essential oils are highly concentrated and can be too potent for direct skin contact. 
• Carrier Oils: Carrier oils (like coconut, jojoba, almond, or grapeseed oil) dilute the essential oil and help it spread more easily on the skin. 
• Patch Test: Before using a diluted essential oil blend, do a patch test on a small area of skin to check for any adverse reactions, always.

Aromatherapy, using essential oils, can be used during pregnancy for various benefits like reducing nausea, anxiety, and insomnia, but it's crucial to use them safely and under the guidance of a healthcare professional.

Some oils are considered safe for use during pregnancy, while others should be avoided or used with caution, especially in the first trimester.