The size and shape of the frontal sinus can vary from person to person. These spaces fill up with mucus, which then drain into the nose.

The draining process can be hindered by blockages. If mucus accumulates, this can cause infections. Bacterial or viral infections are typically located in the frontal or paranasal sinus. Infections can lead to inflammation of the frontal sinus, called sinusitis.

Nasal polyps can also cause sinusitis in the frontal sinus. Nasal polyps are caused by recurring inflammation of the sinuses, such as that resulting from asthma or allergies. They resemble small non-cancerous sacs, and are found in the sinuses or nasal passageways.