What is exercise-induced laryngeal obstruction (EILO)?

People who experience breathlessness during exercise tend to be diagnosed with exercise-induced asthma. However, for some patients, these symptoms are not alleviated by standard asthma treatments. Instead, the cause may be a laryngeal obstruction.

At Guy’s and St Thomas’ Specialist Care, consultant respiratory physician Professor James Hull regularly treats patients misdiagnosed with asthma.

For these patients, exercise-induced laryngeal obstruction (EILO) should be considered. EILO is a reversible narrowing of the larynx that occurs during high-intensity exercise. It impairs airflow, causes shortness of breath, wheezing and often, discomfort in the throat and upper chest.

Compared to asthma or other breathing disorders, EILO is characterised by exercise-induced ‘stridor’, a harsh inspiratory sound due to turbulent airflow through a narrow laryngeal opening.

Symptoms of EILO typically reach their highest point towards the peak intensity of an exercise session and then settle rapidly on stopping exercise.

Fast, accurate diagnosis

This test is called a continuous laryngoscopy during exercise (CLE), and it is not widely available. Guy’s and St Thomas’ Specialist Care is one of only a few centres able to offer a CLE test to patients, carried out by Professor Hull on adult patients, and Dr Samatha Sonnappa on patients under the age of 16.

Access specialist CLE testing

The CLE test is a highly specialised investigation used to diagnose EILO and is available at only a limited number of centres.

Fill in our online enquiry form to arrange a CLE test and speak to our expert team.

Seeing is believing

During the CLE test, our consultant attaches a fibreoptic laryngoscope to specialist headgear, then takes a continuous visual recording of the larynx while the patient exercises.

Firstly, a local anaesthetic gel or spray is used to numb one of the nostrils, then the laryngoscope is gently passed up the nostril to the back of the throat. Some patients may experience a little discomfort in this area, but it does not hurt.

Then, while attached to an electrocardiogram (ECG), patients will exercise on a static bike or treadmill to the point of breathlessness.

Treatments

Once diagnosed with EILO, patients can often control their symptoms with therapies such as improving laryngeal hygiene, ensuring adequate fluid intake, treating nasal problems and using specialist breathing techniques.

However, surgery may be an option for patients who have tried more conservative management therapies and have seen no improvement. In the case of severe supraglottic collapse and pronounced symptoms during strenuous exertion, surgical treatment in the form of a supraglottoplasty may be suggested.

Get an accurate diagnosis for breathlessness during exercise

If you experience breathlessness, wheezing or throat tightness during exercise, it’s important to get the correct diagnosis.

Our specialist respiratory teams offer advanced testing, including the CLE test, to identify conditions such as exercise-induced laryngeal obstruction (EILO).

Complete our online enquiry form to arrange an assessment with our respiratory specialists.

Reviewed regularly to reflect clinical best practice
Last reviewed: 13 March 2026

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