Causes of asthma

Asthma is one of the most common breathing problems and knowing its precise cause can ensure patients receive the most effective treatment available. Our world-leading consultant respiratory physician, Professor James Hull, provides information on the most common causes of asthma and how we can help diagnose and treat it.

The cause of asthma can vary

Asthma is one of the most common breathing conditions worldwide, with over 300 million people estimated to be affected.

The condition causes the airways to become inflamed (swollen), narrowed and often clogged with sticky mucus. This can cause difficulty breathing and prevent those with the condition from taking part in physical activities such as exercise. It can even be fatal in those most severely affected.

The precise reason why some people develop asthma and others do not is still unknown, however we do know certain factors can trigger it. These factors can include allergies, a family history (genetic cause), work-related exposures (such as wood dust or flour) and exercise.

“Determining the precise cause of a patient’s asthma is key to providing the best treatment possible,” explains Professor Hull.

What is allergic asthma?

Allergies – where your immune system overreacts to harmless substances – can result in asthma by causing the muscles around your airways to tighten and become inflamed.

Common allergens which result in asthma can include dust mites (for example, those found in carpets), plant pollen and animal dander (e.g. cat hair).

Asthma caused by allergies is the most common type, causing around 70% of asthma cases in children. This association with allergies decreases in adults, but still accounts for up to 60% of cases.

“The symptoms of allergic and non-allergic asthma are generally the same, making it difficult to determine the type. However, we have some of the most advanced diagnostic tests available at our centre, including FeNO, exercise testing and specialist allergy testing,” explains Professor Hull.

“These tests help us determine the key underlying factors, so that we can review and optimise your treatment. In modern day asthma treatment, we are trying to identify certain patterns of inflammation in the airways so that we can then use the best and most targeted therapies.”

Asthma associated with exercise can be misdiagnosed

It is very common for people who experience breathlessness whilst doing exercise to be diagnosed with exercise-induced asthma. However, asthma is not always the cause, making medications used to treat it ineffective.

Instead, the cause may be a condition called ‘exercise-induced laryngeal obstruction’ (EILO). EILO is a reversible narrowing of the larynx – also called the ‘voice box’ – that occurs during intense physical activity.

This narrowing causes a significant reduction in air flowing to the lungs and the associated difficulty in breathing. It is most common in girls and young women under 20 but can affect any age group and gender.

Thankfully, it can be effectively treated, but determining whether it is EILO or exercise-induced asthma can be a challenge and requires a referral to a specialist.

“To determine whether a patient has EILO, we use a sophisticated test called ‘continuous laryngoscopy during exercise’. A local anaesthetic gel or spray is first used to numb a patient’s nostrils, before a thin tube-like camera is lowered gently into the voice box while the patient exercises,” explains Professor Hull.

Once diagnosed with EILO, patients have a number of treatments available to them, including specialist breathing techniques. Sometimes, surgery may also be recommended if non-invasive treatments do not work.

Get in touch

If you have asthma and would like to find out its precise cause for the best treatment, we can help. Please get in touch with our customer services team to book an appointment with our world-leading respiratory consultants.