If you can get your hands on a bottle of lavender or cardamom extract, you're well on your way to improving your mood, your health, and your immune system, according to a series of scientific studies.

These essential oils, derived from plants, can be used at home to create a relaxing aural experience while simultaneously treating a variety of ailments.

It's a method that goes way back: a smattering of ancient civilizations, from the Egyptians to the Romans and the Chinese, have all used them for healing purposes.

Scent receptors in your nose send messages to the amygdala and hippocampus (parts of the brain) that affect emotions and memories. The theory is that scent can influence these areas, and that some oils, like lavender, can soothe in the way that medications do when stimulating cells in certain parts of the brain.

Beware, though: many lotions, candles, and the like labeled as aromatherapy aren't the real deal. For aromatherapy at its most pure, stick with the essential oils. You can the oil in a myriad of ways:

Here are some of the most popular oils:

This one is often used to reduce anxiety, alleviate constipation, cramps, and headaches, aid with insomnia, and improve circulation.

Inhale this one, straight up. It's said to be great for alleviating stress and good for your skin.  It's also widely used to treat urinary tract infections.

This one is kind of a grab bag. The flowery oil is used to boost libido, treat depression after childbirth, treat addiction issues and respiratory issues, and alleviate tension. Note: pregnant women should avoid this one.

This is the mac daddy of medicinal oils. Bergamot is believed to stimulate the liver and spleen to help with digestion, soothes skin ailments like eczema and psoriasis, and is also used treat depression and anxiety. Note: Stay out of the sun with this one on, or it will burn.

If you need a boost, this is the oil for you. Just a couple of whiffs could help you become more alert and energized. It's also a mood booster, and is known to help calm irritated skin (and mood) and help folks breathe easier.

The most popular calming agent around–it soothes, heals, and relaxes. Bonus: it's also been known to help eliminate acne.

You've most likely come across this in cold remedies and cough drops, and for good reason. Distilled from the leaves and twigs of Eucalyptus trees, this extract decongests and has antiseptic and anti inflammatory properties. Rub this one in when you've got a headache, fever, or stuffy nose. Lavender has almost identical properties, if you prefer a less intense scent.