Where Does All the Phlegm Come From? A Clinical Reflection on Chronic Cough and Airway Sensitivity
A few days ago, a woman in her late sixties came to see me.
Her complaint sounded simple: a cough.
She told me that she had attended a large event in March and developed a cold afterward. At the time, she had a mild fever and a cough. Within about ten days, most of her symptoms had resolved, and she was even able to go hiking again.
By all appearances, the illness seemed to be over.
However, in early May, the cough returned, and this time it was worse.
The most troublesome period was not during the day or at night. It was every morning after waking up.
She described it in a very vivid way:
“Dr Huang, every morning feels like taking out the rubbish.”
She would sit there coughing continuously and bringing up large amounts of phlegm. After the phlegm was cleared, she would feel much better.
When I first heard this story, my initial thoughts were probably the same as many other clinicians.
Could it be sinusitis?
Post-nasal drip?
Chronic bronchitis?
Excess mucus trapped somewhere in the lungs?
After all, when an elderly person is producing that much phlegm every day, those explanations seem reasonable.
Yet several details made me pause.
She rarely coughed during the night. Her daytime symptoms were relatively mild. The problem was concentrated almost entirely in the morning.
Her GP had examined her lungs and found no evidence of pneumonia.
Apart from the cough and phlegm production, she had no significant wheezing, no obvious shortness of breath, and no chest pain.
The pattern did not fit neatly into the typical picture of chronic lung disease.
A Question That Made Me Stop
Three days after her first treatment, she returned for a follow-up visit.
As soon as she sat down, she said:
“Dr Huang, I’m much better.”
I asked her how much phlegm she was still producing.
She replied:
“Before, maybe seventy to eighty millilitres every morning. Now probably only five to ten.”
In her own estimation, she felt about 70–80% improved.
What struck me was not the improvement itself.
Instead, another question came to mind.
If that phlegm had truly been sitting in the sinuses, bronchi, or lungs all along, why would it decrease so dramatically after a single treatment?
Where did it go?
Did one treatment really dissolve seventy or eighty millilitres of mucus?
Honestly, I find that difficult to believe.
And this was not the first time I had encountered a patient like this.
Was All That Phlegm Really Sitting There?
Many years ago, I treated a woman who worked in a shopping mall.
She had a very unusual pattern.
Whenever her coughing episodes started, she had to run to the restroom. Once there, she would spend several minutes coughing and spitting out large amounts of phlegm. Only after clearing it would she return to work.
After several acupuncture treatments, both the coughing and the phlegm production improved significantly.
That case made me wonder:
Was all of that phlegm truly sitting there waiting to be expelled?
Or was some of it being generated during the coughing process itself?
Later, I thought about something most of us have experienced.
On a cold winter day, a gust of cold air hits your nose. Suddenly, you start sneezing. One sneeze becomes several. Your nose begins running continuously.
But was all of that nasal discharge already stored inside the nose?
Probably not.
A more likely explanation is that cold air stimulates the sensory nerves of the nasal mucosa. Once stimulated, the glands begin producing more secretions.
The more irritation, the more secretion.
The more secretion, the more symptoms.
Could coughing and phlegm sometimes work in a similar way?
Could Coughing Become a Self-Reinforcing Cycle?
Over the years, I have increasingly felt that for some patients, the primary problem may not be the phlegm itself.
Instead, it may be an overly sensitive reflex system.
A small amount of irritation.
A slight tickle in the throat.
A tiny amount of mucus.
Even a little cold air.
Any of these may trigger prolonged coughing.
The coughing itself then irritates the local tissues and glands.
The irritation increases secretion.
More secretion leads to more phlegm.
More phlegm triggers more coughing.
The coughing further stimulates secretion.
A cycle develops.
The throat becomes irritated.
The patient coughs.
Secretions increase.
More mucus is produced.
The patient coughs again.
Further irritation occurs.
Even more secretion follows.
Eventually, the patient sees only the end result:
“Why do I have so much phlegm?”
Yet perhaps the phlegm is not the entire story.
In some cases, it may simply be one part of a larger feedback loop.
From a “Phlegm” Model to a “Sensitivity” Model
In recent years, I have increasingly viewed many conditions through the lens of the nervous system.
Headaches.
Dizziness.
Hand numbness.
And perhaps some chronic cough patients as well.
The upper airway, throat, and nasopharyngeal region are richly supplied by sensory nerves, including the trigeminal nerve, glossopharyngeal nerve, and vagus nerve.
When these pathways are repeatedly stimulated over time, their response threshold may become lower.
Stimuli that would not bother most people can trigger symptoms in sensitive individuals.
What causes another person to cough twice may cause someone else to cough for twenty minutes.
What feels like a trivial amount of mucus to one person may feel overwhelming to another.
As a result, my clinical thinking has gradually shifted.
Years ago, when I saw excessive phlegm, my first thought was how to reduce the phlegm.
Today, I am often more interested in whether the reflex system itself has become overly sensitive.
In treatment, I frequently pay attention to the neck, occipital region, and neural pathways associated with upper airway reflexes. My goal is not simply to reduce mucus production, but to calm an overactive system.
If sensitivity decreases, coughing may decrease.
If coughing decreases, local irritation may decrease.
If irritation decreases, secretion may decrease.
And if secretion decreases, the amount of phlegm may naturally fall as well.
At least theoretically, this could be part of the explanation.
My Reflection
At this point, I must remind myself of something important.
These thoughts remain observations, not conclusions.
From a clinical perspective, this patient was already in a recovery phase when she first came to see me.
Her fever had resolved. Night-time coughing was minimal. Daytime symptoms were already improving. The main remaining complaint was excessive morning phlegm.
Therefore, when her symptoms improved dramatically three days later, I cannot confidently determine how much of that improvement came from treatment and how much resulted from the body’s own healing process.
Recovery is rarely driven by a single factor.
Better sleep may help.
More rest may help.
Dietary changes may help.
Weather changes may help.
And sometimes, time itself helps.
The body’s natural repair mechanisms are often underestimated.
To attribute all improvement solely to treatment would not be scientifically rigorous.
Over the years, I have become increasingly aware of another risk.
When a clinician spends years studying a particular concept, there is a temptation to interpret every problem through that same lens.
In my case, I have spent years exploring nerve sensitivity, neural irritation, and functional neurological disorders.
As a result, when I encounter an unusual clinical phenomenon, my first instinct is often:
“Could this be related to the nervous system?”
Sometimes that perspective helps reveal things others overlook.
But it can also create blind spots.
For that reason, I constantly remind myself:
Observation is observation.
Hypothesis is hypothesis.
Conclusion is conclusion.
They are not the same thing.
What interests me most about this case is not whether I successfully treated a cough.
What interests me is the question it raises.
Why can some patients who appear to have enormous amounts of phlegm improve so rapidly?
How much of that mucus was actually present beforehand?
How much may have been generated as part of an ongoing reflex process?
And what role does airway sensory hypersensitivity play in this phenomenon?
At present, I do not have the answers.
Perhaps after observing ten, twenty, or thirty similar cases, I will see the pattern more clearly.
Perhaps my hypothesis will prove correct.
Perhaps it will prove completely wrong.
Either outcome is acceptable.
Because clinical progress rarely begins with certainty.
More often, it begins with a phenomenon that we cannot fully explain.
This case did not leave me with a conclusion.
It left me with a question worth pursuing.
Dr Huang’s Clinical Reflections
Many people assume that a doctor’s value lies in providing answers.
The longer I practise, however, the more I feel that a mature clinician’s greatest strength may not be having answers.
Instead, it is the ability to distinguish between:
- What is observed
- What is inferred
- What remains unknown
Medicine often advances not from certainty, but from doubt.
Sometimes an unexplained observation is more valuable than a seemingly perfect explanation.
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