People with sinus congestion due to allergies are known to snore frequently and loudly. Allergies (and snoring!) can be related to the time of year. Causes of seasonally related allergies are airborne particles (such as pollen) from grass, ragweed or outdoor mold. Year round allergies may be caused by indoor mold, pet dander and dust mites found in items such as carpeting or mattresses. If you experience chronic sinus congestion as well as nighttime snoring, you may have allergies.