Cinnamon oil has been used as a tonic, tranquilizer, digestive aid, and much more for many centuries.  A good quality cinnamon oil is antibacterial, anti-clotting, anti-depressant, anti-fungal, anti-infectious (particularly for the intestinal and urinary system), antimicrobial, antioxidant, anti-parasitic, antiseptic, antispasmodic, antiviral, cleansing, immune boosting and warming to name a few. 

Cinnamon will kill airborne bacteria as well as bacterial infections.  Diffusing it into the air you breathe can help with asthmatic symptoms as well as help in boosting and supporting immune function.  Cinnamon regulates blood sugar and its warming nature may increase circulation, blood flow to the brain and energy levels when used aromatically.

Cinnamon oil kills mold, mildew and fungus.  It fights pneumonia, typhoid, and inflammation.  Cinnamon bark oil is extremely effective at killing gram negative and positive bacterial strains including H. Pylori.

Cinnamon is rich in the essential minerals manganese, iron and calcium, while also having high fiber content.  It removes impurities in the blood and improves circulation.  Combine this with its anti-inflammatory properties and you have a wonderful tool for soothing muscle or joint stiffness and arthritis. 

Research has proven that cinnamon oil obtained from the leaves and twigs of cinnamon can be used for controlling mites that negatively affect honey bees.

That being said, cinnamon oil makes a great mosquito repellent.  It also has the proven ability to boost brain activity.  Due to the strength of this oil a cautious approach should be used.  For topical applications it should be diluted to avoid irritation.