person coughing with mucus in the background

What Causes Asthma Cough Reflex and Throat Clearing? 

About 57% of asthmatics cough.1 Sometimes it’s the first sign of an impending asthma attack. Sometimes it’s chronic, or seemingly always there. Sometimes it’s the only symptom experienced. So, what causes an asthma cough? Here’s what to know.

Throat clearing is another common symptom, often going hand-in-hand with coughing. Some asthmatics clear their throats often. This may also cause throat irritation and hoarseness. The cause of all these symptoms is probably the same: the asthma cough reflex.

What is the asthma cough reflex?

Nerves line your airways. Cough receptors are in your upper airways. This includes your larynx and pharynx. These nerves respond to certain irritants. When this happens, they send signals to your cough receptors. This induces a cough reflex.2-4

These irritants may include things you inhale. Examples include respiratory viruses or microscopic particles. They may also include things within your own body. These include nasal drainage and even asthma.

Your cough receptors receive the signal. They, in turn, send signals to the cough center of your brain. It’s in your brainstem. It sends signals to the muscles of respiration. Inspiratory muscles contract, thereby causing you to take a deep breath. Expiratory muscles contract, thereby causing you to forcibly exhale. The force here is quite powerful. It can reach up to 300 mmHg.2-4

The goal is to force out foreign particles. Some of these particles may be balled up in sputum. So, this sputum is brought to the back of your throat. It can then be swallowed to be dissolved in stomach juices. It can also be spit-up.

What causes the asthma cough reflex?

There are many things that can trigger a cough in asthma. However, here are some of the most common causes.

Sputum

Asthmatics have an abnormally large number of goblet cells, which are cells that produce sputum. So, increased sputum is an early warning sign of asthma. It may irritate the cough reflex as it enters your upper airway. The treatment here would be asthma medicines. It can be prevented by working with your doctor and obtaining good asthma control.

Bronchospasm

Bronchial smooth muscles are wrapped around airways. These muscles are lined with nerves. Bronchial smooth muscle contraction may irritate these nerves. They, in turn, send signals to the cough receptors. This causes you to cough. The treatment here would also be asthma medicines. Obtaining good asthma control may help prevent it.1

Enhanced cough reflex

Very few asthmatics have this. But, about 1-2% have a subgroup of asthma called cough variant asthma (CVA). It’s possible they may have an enhanced cough reflex. The theory is that it’s caused by prostaglandin E2 (PGE2). This is a natural bronchodilator. But it also activates sensory nerves. In this way, it can make the cough reflex more sensitive than normal.1,5-7

Keep this theory in mind! I will discuss it in more detail, along with potential treatments, when I write about CVA.

Postnasal drip

An old name for this is chronic catarrh. It’s inflammation of the nasal passages. This inflammation irritates goblet cells in your nose so they produce mucus that drips down your throat. This mucus irritates your cough reflex. It may also cause throat clearing. This throat clearing may also be chronic. A common cause of asthma is allergies. Colds can also cause it. Potential treatments may be cold or allergy medicine. There may also be other treatments.1

Other

Gastrointestinal reflux (GERD) is another potential cause. This is when stomach juices creep up your esophagus. Micro samples of these juices enter your airways. This can trigger the cough reflex. It can cause throat clearing. Treatment, in this case, would be medicine to treat GERD.

What are the manifestations of coughing?

Asthma cough reflex and throat clearing are common phenomenons. Usually, they go away on their own. Most people self treat and don’t seek medical attention. However, sometimes these symptoms become chronic, which is defined as coughing or throat clearing that persists for 8 or more weeks. This is usually when people seek help. The best path to finding the best treatment options begins by seeing a doctor and getting a proper diagnosis.

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