One of the main causes of sinus drainage is simply being alive. Every day the human body produces several liters of sinus fluid and mucus, and all of that natural liquid must go somewhere. In the case of sinus drainage, fluid from the nasal passages and sinuses drains into the back of the throat, where it is swallowed several times a minute. Eventually, most normal drainage is eliminated through the kidneys as part of a person's urine. Abnormal types of drainage, however, can be caused by factors such as bacterial infections, viral infections, allergens, acid reflux disease, irritating fumes or dehydration.
Some people may experience sinus drainage in the form of a runny nose after eating spicy foods or inhaling an irritating odor. Mucus-producing glands in the nasal area react to such irritants by increasing their production of a watery liquid similar to saliva in texture. By flooding the affected area, the body hopes to wash away the irritants and reduce the inflammation they trigger. This type of drainage is generally thin and clear, and flows freely down the back of the throat or out of the nasal passages. Once the irritant is gone, the drainage generally returns to normal.
Another cause of abnormal sinus drainage can be a bacterial or viral infection, most likely a cold or flu. The amount of infected sinus fluid overwhelms the natural drainage system, so it stagnates in the nasal passages and becomes thicker. This thicker mucus trapped in a dark, moist environment is an ideal feeding ground for bacteria, which in turn causes discoloration and a foul odor. The infected mucus slowly drains into the throat and upper chest, creating even more opportunities for bacterial or viral growth. Cold and flu medications often contain an ingredient which interacts with mucus chemically and thins it for improved drainage. Sinus medications also attempt to reduce the swelling of sinus passages, which in turn creates better drainage.
Sometimes the body reacts to dehydration by limiting the amount of available fluid to mucus-producing glands. If a person has gone several hours without replenishing his or her water levels, the result could be abnormal sinus drainage. Some people may associate this nasal drip with the onset of a cold or allergy, but in reality it is a signal to rehydrate. Proper hydration with fluids other than alcohol or caffeinated beverages should help reduce this kind of drainage.
Allergens such as dust and pollen can also trigger abnormal sinus drainage. The nasal passages become irritated or inflamed in reaction to a known allergen, then begin to swell. The body's natural reaction is to produce more mucus in order to flush out the irritant. Ordinarily, this excess fluid would drain into the throat for elimination, but the throat often swells during an allergic reaction. The excess fluid becomes thicker and discolored by the allergens, causing an unpleasant sensation of fullness in the sinus cavities. This form of sinus infection, or sinusitis, can trigger a painful sinus headache and either excessive sneezing or a runny nose. Allergy medications containing antihistamines may be more effective than decongestants for this type of allergy-induced sinus drainage.
Experts suggest that maintaining proper hydration and avoiding exposure to known allergens can reduce the severity and duration of sinus drainage. Sufferers should also know the difference between drainage triggered by infections and that triggered by allergens or irritants. Decongestant medications work best on infection-based drainage, while antihistamines may produce better results with allergy-based incidents.