You have been coughing for weeks and you're wondering why it's not going away. You tried a cough syrup, which barely did anything. Maybe you even took antibiotics but the cough persisted anyways. Why is this happening?
To get to why, we have to first understand what cough is and why we cough.
What is a cough?
A cough is a reflex. When something irritates our throat, our nerves send a message to our brain. Our brain interprets the signal as an irritant and sends a signal to the muscles in our chest and abdomen to contract, in an attempt to expel the irritant.
Why do we cough?
Fundamentally, we cough due to a few reasons:
There’s an irritant in the throat
The nerves aren’t functioning properly.
The brain isn’t functioning properly.
The muscle isn’t functioning properly.
It’s very rare that we cough due to improperly functioning nerves, brain or muscles. For this reason, we won’t focus on these reasons here. Instead, lets focus on the most common reason: There’s an irritant in the throat.
What’s causing the cough?
If there’s an irritant in the throat, it must be coming from somewhere. We can break the causes down anatomically to these reasons:
The irritant is coming from above the throat
The irritant is right at the throat
The irritant is coming from below the throat
What if the irritant is coming from above the throat?
The most common irritant that can continuously come from above the throat is mucus. When this happens, it’s called post-nasal drip. Post-nasal drip is one of the most common causes of lingering cough.
Post-nasal drip is when the mucus in our sinuses drip down the back of our throat to cause a cough reflex. This often happens after we get upper respiratory tract infections, when the sinuses produce mucus due to inflammation. Even when the respiratory infection has resolved, our sinuses can remain inflammed and continue to produce mucus. Cough that’s caused by post-nasal drip is often triggered by lying down, because it tilts your head and causes mucus to drip down your throat. People can notice a cough at night, because we sleep lying down.
Post-nasal drip does not require treatment per se and can often go away on its own, though this may take weeks to happen. Using nasal saline rinses can help to resolve this faster. Hydrasense and Salinex are examples of common nasal saline rinses.
What if the irritant is right at the throat?
In some cases, you could have persisting infection, in which case there’s inflammation happening right at the throat. It is rare to have persisting throat infections in healthy people who have been treated with antibiotics. But it can happen if it’s resistant to the antibiotics or if it’s not something treatable with antibiotics, such as viruses.
In other cases, you could just have what’s called a “prolonged postinfectious cough”. Which just means a prolonged cough after an infection has resolved. Some pathogens are more likely to cause this, notably COVID-19 and pertussis.
But if you think there could be persisting infection, consider seeing a doctor in person.
What if the irritant is coming from below the throat?
The throat leads down to the stomach. Sometimes stomach acid can flow backwards up into the throat, causing coughing. This upward flow of stomach acid is known as acid reflux, or gastroesophageal reflux disease (GERD).
Cough caused by GERD is often triggered by eating too much or lying down. Similar to post-nasal drip, people might notice the cough most often at night when lying down. An analogy is water in a flask. If you turn the flask 90 degrees, the water is going to go up the neck of the flask. One of the things you can do to reduce GERD is by propping pillows beneath your upper back and your neck, so your neck is at an incline.
Asthma and COPD are other causes of persisting cough, and it occurs when we get irritation our lungs. Usually these people already know they have asthma and COPD, and have already been taught what to look for and what to do by their doctor.
If you have a lower respiratory infection such as pneumonia or bronchitis, this can also result in a cough. Usually persisting symptoms would be more likely caused by atypical pneumonia rather than the classic pneumonia, but we won’t go into the details here since it’s beyond the scope of this article. In these instances, symptoms typically get progressively worse. Whereas with something like post-nasal drip, symptoms typically get progressively better.
If you recently started a blood pressure medication belonging to the ACE (Angiotensin-Converting Enzyme) inhibitor or ARB (Angiotensin Receptor Blockers) class of medication, it could be causing the cough as a side effect. This one’s usually obvious because your cough started right after you began taking the medication.
What else should I keep in mind?
Keep in mind that these are the most common causes seen in healthy populations. Is it possible it could be cancer, interstitial lung disease, heart failure or TB? Yes. But for most healthy people, those possibilities are very unlikely. If you’re worried or have questions, send us a message at plumfin.com.
References
Weinberger SE, Saukkonen K. Causes and epidemiology of subacute and chronic cough in adults. In: Barnes PJ, King TE Jr, eds. UpToDate. Waltham, MA: UpToDate Inc. Updated July 27, 2023. Accessed October 25, 2024.
Hui D. Approach to Internal Medicine: A Resource Book for Clinical Practice. 3rd ed. Springer; 2015.
