The sinuses are a combination of large and small air pockets in the face. They are connected to the inside of the nose through small openings called ostea. They help to optimise the temperature and humidity of the air reaching the lungs. The sinuses can become infected due to a variety of reasons. The symptoms usually associated are nasal obstruction, facial congestion, headaches, excessive catarrh, disturbance in the sense of smell and toothache.