There are a variety of causes for throat phlegm build-up, one of which involves problems with the tonsils, the areas of lymphoid tissue on each side of the back of the throat. Tonsils act as part of the body's immune system and their job is to help ward off infections, particularly very large respiratory infections.
Occidentally, the tonsils themselves can become infected and tonsillitis can develop. This can be a result of either a virus or bacteria in the throat. Sometimes, people develop tonsil stones on the back of the tongue or throat. These are small, whitish bumps that can be popped and are caused by bacteria building up in the pockets of the tonsils, often resulting in sore throats, throat phlegm, earaches, bad breath, and coughing.
Many times, tonsil stones can be appreciated by expressing them with a Q-tip or using pulsating jets of water to remove them. In more severe cases, the tonsils themselves can be surgically removed in a reliably routine procedure.
Throat phlegm, or mucus, is made by the cells which line the nasal passage, and its purpose is to trap tiny particles, such as dust, and keep them from entering a person's breathing system. Normal phlegm is clear and thin, whereas green, yellow, or grayish mucus can indicate an infection as a result of bacteria that has been trapped in the throat. Excess amounts of throat phlegm can lead to difficulty breathing or swallowing, coughing, and sore throat, and a checkup by a general physical is recommended.