Healthy phlegm or mucus is usually thin and clear, and so we tend to assume if we’re producing clear phlegm, or clear snot, there is no infection or illness present. The truth is that clear phlegm can be a symptom or side effect of certain infections and illnesses. These infections are usually viral in nature, which means antibiotics are not necessary. Some of the most common viral infections that produce clear mucus include sinus infections, the common cold, and influenza. Usually, your body will fight these infections on its own, but you should see your doctor if other severe symptoms are present and persist.
You can experience clear phlegm during either a viral or a bacterial infection, but clear mucus is more common during viral infections. For example, you might produce clear mucus if you have a sinus infection that is not bacterial in nature. If this is the case, the mucus might also be sticky or glue-like and you might have swollen and tender sinuses and nasal passages. If the bacteria become trapped in the nasal passages, the sinus infection might become a bacterial infection. When this happens, your mucus can become yellow or green and it might become thick or clumpy.
Other kinds of infections that produce clear mucus include the common cold and influenza. Both of these infections are viral infections, and both can cause you to produce an excess of clear mucus that is present in your nose and the back of your throat during the beginning and ending stages of the illnesses. During the first few days of contracting a cold or flu, your phlegm will probably be thin and clear and you might have a runny nose. Once your body starts responding to these infections, though, your phlegm might become yellow or green and even change consistency. Later, once your immune system is closer to eliminating the infection, the mucus will become clear again.
Since clear phlegm is more commonly present with viral infections, usually you do not need antibiotics to treat them. If the symptoms are particularly severe, your doctor might prescribe medication to treat the sinus infection or manage the cold or flu symptoms. Otherwise, over-the-counter medications are usually effective in managing the symptoms until your body’s immune system fights the infection. Always seek medical attention if the phlegm becomes discolored or if it is accompanied by severe symptoms such as pain, chills, or a fever.