Lavender - relaxation and sleep. To be exact, lavender tends to increase the alpha waves in the back of your brain, says Hirsch, leading to increased relaxation. Lavender has also been shown to reduce anxiety and, according to Hirsch, studies reveal that the number one odor that enhances male sexual arousal is a combination of lavender and ... pumpkin pie! (Combining the scents of cucumber and Good & Plenty candy does the same trick for women. Go figure!)

Peppermint - alertness! If you need to wake up from your sleepy post-lunch stupor, peppermint stimulates your trigeminal nerve, also known as your "irritant" nerve (the same one that makes you cry when you cut an onion). This stimulation, explains Hirsch, projects directly to the part of your brain that keeps you awake and alert. As SELF reported in September, studies have also shown that peppermint can help increase your exercise performance, so a whiff before heading to the gym can boost your workout! 

Eucalyptus - empathy. Like peppermint, eucalyptus can help wake you up. But, fascinatingly, when combined with menthol and camphor, Hirsch says eucalyptus enhances empathy. Read SELF's report on the amazing powers of empathy and how it can improve everything from your work life to your friendships here. 

Spicy mixed floral - learning. Hirsch points to a study that showed a spicy mixed floral odor increased participants' speed of learning by 17 percent. Perfect for prepping for a meeting or a job interview (or studying up on your next far-flung vacation destination!). Studies done by the the Smell & Taste Treatment and Research Foundation also show that when smelling a spicy mixed floral, men were more likely to underestimate the weight of a female model. Something to keep in mind the next time you're not feeling up to your skinny jeans!

Green apple - anxiety relief. The scent of green apple might evoke associations of springtime, but in one study, it also helped to decrease the anxiety and claustrophobia felt by people who had been placed in, as Hirsch describes it, "coffin-like tubes." So the next time you're in a tight situation (figuratively or literally!), green apple can help relieve some of your anxiety.

Jasmine - athletic performance and reaction time. Participants in studies conducted by Hirsch's team who wore surgical masks coated with jasmine had faster reaction times when performing reflex-measuring tasks than other participants. Hirsch says because of this, jasmine could also prove useful during physical therapy. And you thought it just smelled exotic!