Sinuses are simply cavities in your head which are connected by narrow passageways. The sinuses make mucus that drain out of your nose. Similar to ear block, these passages can become blocked by inflammation or an excessive amount of mucus production.
When the sinuses are unable to equalize to the outside air pressure, they become blocked. This can be incredibly painful. Symptoms include:
It is important to always stay hydrated, especially before and during a flight. This will help to thin the mucus in the sinus cavities and promote discharge.
Additionally, avoid anything that could cause an allergic reaction, as this will cause the sinuses to become inflamed.