Among the most common causes of sore throat and phlegm are colds and other viruses, though bacterial infections may cause these symptoms as well. In other cases, allergies are at the root of such symptoms, and lifestyle choices such as smoking cigarettes may also lead to a sore throat and phlegm. A person may even develop these symptoms after being exposed to secondhand smoke.

One of the most common causes of sore throat and phlegm symptoms is a common cold. Often, a person experiences a sore throat as one of the first indications that he has a common cold, and phlegm frequently develops later in the course of the illness. Some people assume that the presence of phlegm means a person has a bacterial infection instead of a cold. A person may be particularly likely to make this assumption if the phlegm is discolored rather than clear. In reality, however, discolored phlegm can also develop as the result of a virus, including the common cold.

Other viruses may cause sore throat and phlegm production as well. For instance, a sore throat is one of the common symptoms of a case of influenza. Often, a person who develops the flu starts out with a dry cough that does not produce much or any phlegm. Later in the illness, however, a person may start to notice the presence of phlegm as well. Additionally, both of these symptoms may develop when a person has a flu-like illness rather than the flu.

An individual may also develop a sore throat and phlegm in relation to allergies that affect the respiratory system. Many people are aware that allergies can cause a person to feel a tickle in his throat or develop a cough, but allergy signs can mimic some of the symptoms of a common cold as well. In fact, a person with an allergy may sometimes have a sore throat that lasts longer than it would with a common cold. He may also develop a cough that produces phlegm whenever he has significant exposure to an allergen.

Sometimes a sore throat and phlegm are unrelated to an illness, but develop because of something the affected person does. A prime example of this is the sore throat and coughing that may accompany cigarette smoking for some people. For example, smoking can irritate the smoker’s respiratory passages and lead to a sore throat and phlegm. This may be compounded if the individual also has a cold or allergies. Additionally, some people may develop these symptoms when they are exposed to secondhand smoke.