In accordance with the motto of this year’s World Asthma Day, “Uncovering Asthma Misconceptions”, this is the sixth post of our mini-series about asthma based on our patient booklet “Fast Facts for Patients and their Supporters: Asthma”. After a thorough review it may become clear that your asthma is not only difficult to control but what is called severe asthma.

What Is Severe Asthma?

Severe asthma does not respond to the usual treatments, even high-dose inhaled steroids and a second preventer medication. It is sometimes called severe refractory asthma. About 4–8% of people with asthma have severe asthma.

Most people with severe asthma take a high-dose inhaled steroid and a high-dose long-acting reliever as prescribed, yet still have asthma symptoms and frequent asthma attacks.

What Is the Cause of Severe Asthma?

We do not yet know why some people get asthma and some people get severe asthma. It may be that more than one disease is working at the same time to cause a type of airway inflammation that does not respond to steroids. Severe asthma often coexists with gastroesophageal reflux disease (a type of heartburn), rhinitis or sinusitis (types of nasal congestion).

You can develop severe asthma at any age. It may develop slowly or be triggered by, for example, a virus or hormonal changes.

How Is Severe Asthma Diagnosed?

If you are taking treatment for difficult asthma correctly but there is no improvement after about 3 months, you will need further tests to try to find out what is causing the airway inflammation.

You are likely to have blood tests, and a sample of cells may be taken from the mucus in your airways. Your test results will show if there are high levels of white blood cells called eosinophils and neutrophils in your blood or mucus.

Sputum Induction

Sputum induction is a painless way of collecting a sample of sputum (saliva and mucus) from your lungs. You will be asked to inhale a fine mist of salty water through a mask, which will irritate your airways and cause you to cough. The sample is collected in a sterile cup.


Alternatively, a mucus sample can be collected with the use of a thin flexible fiber-optic ‘telescope’ called a bronchoscope.

A tube is passed through the nose, down the windpipe and into the large airways of the lung. Fluid is then injected down the tube and sucked out again to obtain washings of mucus from the lining of the airways.

A local anesthetic will be sprayed into your nose and mouth to prevent discomfort and coughing during the procedure. You must not eat or drink for 4–6 hours afterwards, until the anesthetic has worn off, as there is a risk of choking. This procedure usually takes about an hour. You will not need to stay in hospital for it.

The bronchoscopy can also show if there are other cells or lung diseases present.


Other Tests

A FeNO test combined with a blood test called a full blood count can show if you have a lot of eosinophils in your airways. However, FeNO tests can be tricky to interpret, as inhaled steroids and smoking can interfere with the results.

Different Types of Severe Asthma

Eosinophilic Asthma

Eosinophils are white blood cells that normally help you fight infection. Your lungs can become inflamed if you have a high number of eosinophils (high eosinophil count).

This is called eosinophilic asthma (sometimes called e-asthma). There are treatments for eosinophilic asthma.

Non-Eosinophilic Asthma

Non-eosinophilic asthma may be due to a high number of white blood cells called neutrophils. Neutrophils are very important in battling infections and are common throughout the body, but too many of them in the lungs causes inflammation. Your doctor will check the level of neutrophils in your sputum sample.

It is very difficult to treat an excess of neutrophils without hindering the body’s natural response to dangerous infections.

Allergic Bronchopulmonary Aspergillosis

Allergic bronchopulmonary aspergillosis is a very rare type of severe asthma in which a fungus called Aspergillus causes an allergic-like response in the airways. It may even get lodged in the lungs, causing a persistent form of severe asthma.

Severe Allergic Asthma

Severe allergic asthma is caused by a severe allergic reaction to a trigger.


Please check out the previous and the next post of our series here:


Information based on Fast Facts for Patients and their Supporters: Asthma (Karger, 2020).

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