What are the Most Common Causes of Phlegm in the Mouth?

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  • Written By: Anna T.
  • Edited By: Melissa Wiley
  • Last Modified Date: 26 January 2020
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The causes of phlegm in the mouth are often related to allergies and sinus infections. Most of the time, phlegm makes its way into the mouth from the chest and throat because phlegm in the mouth is almost always coughed up from these areas. In most cases, excess phlegm will go away when the root cause is gone. When allergies abate or cold and sinus problems rectify themselves, the amount of phlegm a person coughs up will almost always lessen. People who smoke occasionally cough up lots of phlegm in the mornings, and many people who quit smoking have reported that the excess phlegm disappeared once they kicked the habit.

People who have allergies or cold and sinus problems might end up dealing with phlegm in their mouths. In most cases, phlegm develops inside the chest and lungs when a person has had problems with allergies or sinus infections for an extended period of time. The phlegm is often associated with an infection, and it may be green to brown in color. People who are coughing up phlegm for more than a week may need to see their doctors so the possibility of infection can be ruled out. If a person has been coughing up a lot of phlegm over an extended period of time, he might have developed pneumonia or bronchitis, which the common cold and allergies can occasionally turn into.


Contrary to popular belief, phlegm and mucus are not exactly the same thing. Many people who experience phlegm in the mouth may believe it's just mucus when phlegm is actually the problem. It is often possible to tell the difference between phlegm and mucus by noticing the texture. Phlegm is usually much thicker than mucus and does not originate inside the nose or sinuses as mucus does. Mucus almost always runs out of the nose from the sinus area when a person has a cold or allergies, and phlegm is normally coughed up from the chest or inside the throat.

Coughing up lots of phlegm may be an annoyance for many people, but it is actually helpful. Getting rid of phlegm in the mouth is one way that the body gets rid of infection, and coughing up this excess means that the fluid that has settled into the chest and lung area is exiting the body. When fluid gets inside the lungs and chest and a person does not cough it up, there is a very good chance he will develop pneumonia, which can occasionally be a life-threatening problem.


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Post 4

If I have a dry, itchy cough, mucus is usually involved. When my cough is wet and rises from my chest, then I know I have phlegm.

One of the worst cases of phlegm I have ever experienced happened after I inhaled a lot of dust and dirt. I was cleaning out my outdoor utility room, which had layers of dust on the shelves, and I had neglected to wear a mask.

As soon as I started wiping down the shelves, the dust flew up into my face, and before long, I had begun coughing. Later on that night, the irritants in my lungs had caused all kinds of phlegm to develop, and I was coughing it up on a regular basis.

I really needed to cough all that stuff out in order to get better. So, I just let it run its course. The phlegm captured the dust particles and helped transport them out of my body.

Post 3

Sometimes, a strep throat infection can go into your lungs and cause you to start coughing up phlegm. Even though I went to my doctor and got antibiotics and steroids to treat my strep throat, I still wound up getting bronchitis.

The sore throat seemed to go away for a couple of days while the steroids were doing their thing, but once I stopped taking them, I developed a horrible cough. I had so much phlegm in my airways that it was hard to breathe.

I got some different medication from my doctor and used a humidifier in my room at night. She gave me some cough syrup with codeine in it that helped tame the phlegm cough long enough for me to sleep. I think that finally getting some rest made a huge difference in my recovery period.

Post 2

@seag47 – It sounds like you have the same problem I have. Post nasal drip has plagued me for years, and it's all due to my allergies.

I take an antihistamine every day, but it can only do so much. Thankfully, my sinus drainage doesn't develop into anything more serious on its own. However, when I have a cold, that's a different story.

When I have a cold, I have so much mucus that it just can't stop flowing. Almost always, I will start coughing up phlegm from my chest. I know it's there because I hear a wheezing and rattling when I breathe.

Post 1

I always thought that mucus and phlegm were the same thing. I assumed that the mucus in my throat that had drained down from my nose was phlegm. Even though it comes out when I cough, I know where it is coming from, and it's definitely mucus.

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