What is sinus?

Sinus cavities are like small water pockets in the head. Any air, dirt or dust is not inhaled directly by us. The dirt sticks in this mucus, hair in nostrils and only fresh oxygen goes into your body and lungs and so on. This is just one of uses of sinus. So as i said, these sinus cavities or water pockets gets inflamed or blocked when there is too much dust, allergy, due to cold or sinus then you will start breathing less oxygen (you wont notice the difference but you are breathing less). In most cases, after sometime it should become normal, see the below diagram of our sinus cavities.

They are all connected. If you drop oil in ears, it comes out from your mouth or nose. If you drop oil in nose, it come through ears or mouth. Google, you have seen people do squirt milk from eyes etc(Guinness even has a record for it) . Its not magic. Its human anatomy. Yes, hard to believe.