Asthma: Causes, Symptoms and Treatment

Asthma makes breathing difficult. It affects over 330 million individuals worldwide and causes approximately 1000 deaths daily, according to the Global Asthma Report 2018. In Hong Kong, about 10% of children and 5% of adults are asthmatic, which means more than 330,000 citizens suffer from it. 

What is Asthma?

Asthma is a common chronic respiratory condition caused by inflammation. The inflamed airway becomes hyper-responsive to triggers. The muscles surrounding the airways subsequently tighten up, resulting in narrowing and swelling of the air passages.  The inflammation also stimulates sticky mucus secretion. Airflow is therefore impeded, which leads to wheezing, breathlessness, coughing and tightness in the chest. 

Asthma can develop at any age and often starts in early childhood. It is reported that around 50% of patients have experienced symptoms of asthma before the age of 10.  More boys are affected during childhood, while it is more prevalent and severe in adult women. 

Despite remaining an incurable disease, asthma can effectively be controlled by drugs and other forms of management. Airflow obstruction is reversible either with medication or sometimes occurs spontaneously.

Types of asthma 

There are two main types of asthma:

  • Allergic asthma: it is triggered by allergens such as dust mites, mould and pollen. Most allergic asthma sufferers are children. It can be hereditary. Patients often show symptoms of other allergic diseases such as eczema and allergic rhinitis. Avoiding any known allergens can improve the symptoms. 
  • Non-allergic (endogenous)  asthma: it is caused by factors other than allergens, for example, smoke, cold air, stress and viruses. Most cases are seen in middle-aged or older adults.  It is usually not hereditary and is more common in women than in men. 

Asthma can also be classified into other types, for instance: 

  • Occupational asthma: it is caused by inhalation of substances at the workplace such as chemicals and fumes. Workplaces with a higher risk of causing occupational asthma include bakeries, hospitals and clinics, pet shops and farms. 
  • Seasonal asthma: symptoms occur at a particular time of the year, for instance, in the springtime due to pollen, or the wintertime due to cold air.
  • Exercise-induced asthma: also known as exercise-induced bronchoconstriction, which occurs in response to physical activity.

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Signs and Symptoms 

The clinical features of asthma vary by time, frequency and intensity. They can start gradually or come on as an attack. 

    • Chronic or regular cough that often worsens at night or early in the morning, after exercise or when laughing.  It is a major symptom, present especially in children. 
    • Wheezing, a whistling sound when exhaling air. It is one of the most characteristic symptoms of asthma. 
    • Chest tightness as a result of muscle constriction around the airway.
    • Shortness of breath due to narrowing of the airways, making it difficult for air to move in and out of the lungs, which may reduce oxygen supply to all areas of the body.
    • Increased mucus (sputum) production, which makes breathing even more difficult as mucus plugs can block the airways.

Causes and triggers 

What causes asthma is unknown; however, some environmental and genetic factors may be involved. It is important to identify your personal triggers and avoid them. 

    • Allergies 
    • Inhaled allergens, e.g. house dust mites, animal danders, mould, fungus and pollen. 
    • Cigarette smoke. It also accelerates declines in lung function. Exposure to cigarette smoke during pregnancy also put the child at higher risk of developing asthma. 
    • Air pollutants 
    • Exercise 
    • Cold air 
    • Respiratory tract infections and viral infections, e.g. the common cold 
    • Emotions, e.g. depression, stress or even laughing. 
    • Food and additives, e.g. nuts, eggs, fish, food preservatives and colourings. 

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Diagnosis of Asthma

Your doctor may diagnose asthma by reviewing your medical history. Having allergic conditions such as eczema and hay fever, or having a family history of those conditions or asthma increases the probability. You may be asked to describe your symptoms, time of onset, possible triggers, other medical issues and current medication. 

Physical examination is performed to 

  1. look for the classic signs and symptoms, especially widespread wheeze when you breathe;
  2. check for the presence of atopic (tendency to develop an allergy) diseases; 
  3. rule out other conditions such as chronic obstructive pulmonary disease (COPD) and gastroesophageal reflux disease (GERD). 

Several diagnostic tests are useful in measuring how well your lung functions. 

  • Spirometry: measures the amount of air you breathe in and out and the speed of your breath. This test determines the severity of your asthma. 
  • Peak flow: measures how fast air can move out of your lungs with maximum effort after a deep inhalation. This test can also be done at home for self-monitoring of the condition.

Other tests include 

  • Bronchoprovocation: to measure airway responsiveness by directly stimulating airway muscle contraction using substances such as methacholine. A reaction may suggest asthma. 
  • Exercise challenge: it compares the degree of airflow limitation before and after vigorous physical activity. 
  • Exhaled nitric oxide: measures the amount of nitric oxide that is exhaled from a breath. Increased levels of nitric oxide are associated with swelling of lung airways and may indicate asthma
  • Skin prick/ allergy testing: helps identify asthma triggers for individual patients. 
  • Imaging tests: e,g, chest X-ray, CT scans, MRI and electrocardiogram (ECG) to look for any abnormalities in the lungs and to rule out other causes. 

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Treatment of Asthma

Although there is no known cure for asthma, it can be effectively managed. Treatment plans change over time depending on the severity of the asthma, the response to treatment and the level of control. 

Most medications are delivered by inhalation, allowing drugs to directly reach the affected site and be maximally effective with fewer systemic side effects.  In severe cases, patients may need both oral and inhaled medication. 

Long-term controllers 

These are types of medication that are taken every day to reduce airway inflammation, thereby keeping symptoms and asthma attacks at bay. 

  1. Inhaled corticosteroids

They are the first-line anti-inflammatory medication used in the long-term control of asthma. It is important to note that the response to inhaled steroids will not be immediate and may take from a few days to a few weeks to be evident.

One common side effect of these inhalers is oral candidiasis (thrush), it can be avoided by using a spacer device to deliver the medication from your inhaler, or by rinsing your mouth with water, then gargling and spitting out after each dose. It is reported that chronic use may slightly stunt growth in children. 

Examples: beclomethasone, fluticasone, budesonide

  1. Long-acting beta-agonists (LABA)

These are long-acting bronchodilators that help reduce symptoms by opening tight airways. LABA should not be regularly used by themselves but are useful when combined with inhaled corticosteroids. They should not be used for an asthma attack as they do not act quickly enough and are associated with severe asthma exacerbations. 

Examples: formoterol, salmeterol and vilanterol. 

  1. Leukotriene modifiers 

These types of oral medication open up the airways by counteracting the effects of leukotriene, an inflammatory chemical which causes smooth muscle contraction. Some are available in the form of chewable tablets.

Examples: montelukast and zafirlukast. 


This medication relaxes smooth muscles around the airways and reduces inflammation. It is rarely used nowadays, as newer treatments are more effective and have fewer side-effects. Do not crush or chew the tablet if it is a sustained-release formulation.

  1. Anticholinergics

These are inhaled bronchodilators, mainly prescribed as an adjunctive treatment for severe asthma. Common side-effects are dry mouth and dizziness. 

Examples: tiotropium and ipratropium

  1. Mast cell stabiliser 

They block the release of histamine, which causes a number of the symptoms of inflammation. 

Example: cromolyn sodium. 

  1. Immunomodulators   

They are administered by injection to reduce the immune system’s overreaction to allergens. You may need biologics if you have moderate to severe allergic asthma. 

Examples: omalizumab and mepolizumab. 

  1. Combination inhalers 

Some patients may find combination inhalers convenient to use as they contain both an inhaled corticosteroid and a long-acting beta-agonist. 

Examples: Seretide, Symbicort and Relvar Ellipta

Short-term quick relievers 

There are rapid rescue medications for acute asthma and prevention of exercise-induced asthma. You should carry them with you at all times. 

  1. Short-acting beta-agonists (SABA)

They promote bronchodilation in just a few minutes to provide fast relief. Children aged 5 or under usually take only SABA to treat wheezing. 

SABA can be administered by a nebuliser that creates a mist for breathing in the medication through a mask or mouthpiece. You can also take them using an inhaler with or without a spacer. 

Examples: salbutamol, terbutaline 

  1. Oral and intravenous corticosteroids

These are used for the short-term treatment of severe asthma. Long-term consumption may cause an array of side effects, such as loss of bone density, skin thinning and bruising and redistribution of body fat. However, they can be safe and highly effective when used for rapid control of a severe asthma exacerbation.

Examples: prednisone and methylprednisolone.  

  1. Short-acting anticholinergics 

These are generally less effective than SABAS but are useful for patients who cannot tolerate SABAs. 


Also known as allergy shots, immunotherapy works to reduce the overactivity of the immune system towards allergens. They help patients with allergic asthma. 

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Asthma control 

According to the Global Initiative for Asthma (GINA),  your asthma is considered uncontrolled if you have experienced, in the past 4 weeks, at least 3 of the following:

  1. symptoms during the day more than twice a week. 
  2. disturbed sleep and night-time waking because of asthma.
  3. increased use of quick relievers to more than twice a week.
  4. limitations of daily physical activities due to asthma.

If you found that you are experiencing 3 or more of these symptoms, it is time for you to visit your doctor to review and step up treatment. 

Asthma action plan 

An asthma action plan is a unique written plan prepared by your doctor with your participation. The asthma action plan teaches you

  • how to recognise symptoms of deteriorating asthma. 
  • what medicine to take for each symptom, depending on the severity. 
  • when to seek immediate medical attention. 
  • how to control and avoid triggers. 

Prevention and self-care 

There are several things you can do to improve asthma control. 

  • Avoid any known triggering factors, e.g. keeping your home as dust-free as possible.
  • Adopt a healthy lifestyle, e.g. regular exercise, balanced diet, proper stress management.  
  • Quit smoking.
  • Pay attention to weather changes. 
  • Make sure you know how to use the inhaler correctly. If you have coordination difficulties in using an inhaler, you can use it with a spacer, or use a different format of inhaler.
  • Monitor asthma at home, e.g. keeping a record of peak flow.
  • Have an annual flu shot. Influenza affects people with asthma more severely than others.

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What is the cost of Asthma Treatment in Hong Kong?

Cost of treatment in Hong Kong’s Public Sector:

For eligible persons with a HKID card, the cost for specialist outpatient services in public hospitals is $135 for the first consultation and $80 per subsequent consultation. Each drug item costs $15.  

For non-eligible persons without a HKID card, the cost for attending specialist outpatient clinics is $1190 per attendance in public hospitals. 

Beware of waiting times which can be very long in the public sector.

For details, call the Hospital Authority at 2300 6555.

Cost of treatment in Hong Kong’s Private Sector:

Fees will vary according to the condition of the patient, doctor fees, medication fees, and administration fees of each hospital or clinic. It is best to first consult your doctor and discuss the options suited to your situation. Our research found that the general consultation fee of visiting a Respiratory Medicine specialist ranges from $400 to $1800, excluding drug charges.

* All amounts are in HKD and were last updated in June 2020. No responsibility is accepted for any inaccuracies, errors, or omissions. It is always best to call ahead to make sure the information is still up-to-date.

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Dr. Sarah Borwein is a Canadian trained General Practitioner who co-founded the Central Health Group and has been practicing family medicine in Hong Kong for over 15 years. After obtaining Certification in Family Medicine from the College of Family Physicians of Canada, she completed a Masters degree in Infectious Diseases from the London School of Hygiene and Tropical Medicine. She worked as a staff physician at the Beijing United Family Hospital where she was Director of Infection control during the SARS outbreak in China. A French speaker, Sarah is the advising and referral doctor for the French Consulate in Hong Kong. She is the site director for GeoSentinel (an international disease surveillance network) in Hong Kong and is past President of the Asia Pacific Travel Health Society. In addition, she sits on the Centre for Health Protection's Scientific Committee on Vector-borne Diseases, which advises the Hong Kong Department of Health on this type of illness.

This article was independently written by Healthy Matters and is not sponsored. It is informative only and not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be relied upon for specific medical advice.