The American Academy of Otolaryngology says that the sinus cavity produces between 1 and 2 quarts of mucus a day. The mucus is drained down the back of the throat, going unnoticed. When a person develops excessive mucus in the sinus cavity from the common cold or allergies, it can lead to drainage in the back of the throat, called post-nasal drip. Postnasal drip occurs when nasal discharge accumulates in the back of the throat, leading to a cough, upset stomach and chest congestion. Common causes of sinus drainage in the neck include viral infections, allergic reactions and physical issues.
Viral Infection
The common cold is the result of a viral infection related to one of over 200 different viruses. A viral infection is a common cause of sinus drainage. The virus causes the sinus cavity to become inflamed, irritated and congested. This leads to the blocking of the nasal passages, reducing breathing capacity. A viral infection usually results in postnasal drip because excess mucus cannot drain properly. The mucus may appear to be thick and greenish in color. A viral infection causing sinus drainage may lead to other complications such as bad breath, a chest infection or sinus infection.
Allergic Reaction
An allergic reaction occurs in a person's body when the immune system doesn't recognize a particular substance, such as mold, pollen or pet dander. The immune system overreacts and releases histamine to ward off the intruding substance. The histamine released by the body causes common allergic symptoms such as itchy eyes, hives and nasal reactions. A common nasal reaction from allergies is post-nasal drip. The excess mucus from an allergic reaction will appear to be clear and thin and may cause the person to sneeze obsessively and develop a cough.
Physical Issues
Two of the most common physical causes of sinus drainage in the neck are a deviated septum and nasal polyps. A deviated septum occurs when the center of the nose is crooked, blocking normal air and drainage flow. This condition can be the result of human development or an injury. Nasal polyps also restrict normal breathing and nasal drainage, leading to post-nasal drip. Nasal polyps are non-cancerous tumors that develop along the sinus wall. They are commonly treated with prescribed steroids or surgery.
