Asthma is a relatively common condition. According to a National Health Survey conducted from 2016-2018, approximately 11.9% [1] of Singaporeans aged between 18-60 were affected by asthma at some point of their lives. To better understand what asthma is, let’s first understand how our lungs work, and then we can learn about allergic asthma.
How do our lungs work, and what is asthma?
Breathing is something we do without even thinking, but the whole breathing process is intricate and complicated. When you breathe, air travels down your throat and into your lungs. Within your lungs are tiny airways known as alveoli. Once air reaches the alveoli, it transfers to the surrounding blood vessels and is transported all over your body.
However, when someone has asthma, this process gets affected negatively, at times making breathing difficult. Asthma is a chronic inflammatory disease of the airways in the lungs. It occurs when the airways and surrounding muscles swell and tighten. This causes a significant narrowing of the airways, leading to production of mucus which also contributes to the narrowed airways, making breathing difficult. The severity of asthma varies between individuals ranging from mild irritation to life-threatening.
Types of asthma
Allergic asthma: asthma triggered by various allergens and can be linked to different seasons in seasonal countries.
Non-allergic asthma: air irritants that are not linked to allergens and can trigger non-allergic asthma.
Occupational asthma: asthma triggered by irritants found at some workplaces.
Exercise-induced bronchoconstriction (EIB): asthma trigger by exercise within a few minutes of starting.
Aspirin-induced asthma: severe asthma triggered by aspirin or other non-steroidal anti-inflammatory drugs (NSAIDS).
Nocturnal asthma: symptoms of asthma that worsens at night.
Cough-variant asthma (CVA): characterised by a dry, persistent cough and usually does not result in common asthma symptoms such as wheezing and breathlessness.
For the purposes of this article, we will be focusing on allergic asthma.
Can allergies cause asthma?
Yes, allergic asthma, or allergy-induced asthma, is asthma that is triggered by various allergens. These can range from pollen to even cockroaches; but often allergens that cause allergic rhinitis/hay fever have been known to trigger an allergic asthma attack.
An allergic reaction is caused by an over-reaction of our immune system. The main function of the immune system is to protect our body from dangerous or harmful substances that can make us sick.
However, sometimes the immune system mistakenly identifies harmless substances such as food, dust, pollen or other everyday items as harmful. When this happens, our body overproduces immunoglobulin E (IgE), an antibody when present in excess can cause your airways to:
Become inflamed or irritated
Produce large amounts of thick mucus
Narrow due to tightened muscles that surround the airways
Worldwide, allergic asthma is responsible for 90%[1] and 50% of asthma cases in children and adults respectively.
What are the common causes of allergic asthma in Singapore?
According to Asthma Singapore [2], the common causes of allergic asthma in Singapore are:
Cockroaches: dried droppings and dead cockroaches can trigger allergic asthma.
Dust mites: dust mites and their droppings are common triggers of allergic asthma.
Indoor mould: Singapore is a humid country and so indoor mould is fairly common especially in areas that are wet and humid. The spores produced by mould can trigger allergic asthma.
Pet dander: proteins present in pet dander can trigger allergic asthma. Accumulation of pet fur can also result in other allergens appearing such as dust mites and cockroaches.
Pollen: pollen produced by various types of trees such as the cotton tree can trigger allergic asthma.
How do I know if I have allergic asthma?
If you experience the following symptoms, you may have allergic asthma:
Breathlessness
Chronic coughing especially at night
Wheezing
Chest tightness
Symptoms that you might experience in conjunction with allergic asthma are:
Hives or rashes
Runny nose
Watery eyes
Sneezing
Blocked or stuffy nose
Do I have asthma or just allergies?
One of the best ways to identify if you have asthma or allergies is to figure out where the reaction happens.
If you are experiencing symptoms in just your nose such as sneezing, congestion, watery nose, then chances are that you are having an allergic reaction. However, if you are experiencing symptoms in your lungs such as wheezing, chest tightness, breathlessness, then you are having an asthma attack.
Asthma attacks can vary in intensity and you must ensure that you have a treatment plan ready to help alleviate your symptoms and prevent them from escalating. You are at a higher risk of developing allergic asthma if you:
Have a family history of allergic reactions
Have existing allergies to other substances
How is allergic asthma diagnosed?
Diagnosing allergic asthma is two-fold. First, an allergy test in conducted, then further tests will be conducted to diagnose for asthma.
Allergy test
Skin prick/scratch test: thin needles with 10 to 50 allergens, are used to prick or scratch the skin on your back or forearm. Another way is to place droplets of allergens onto the pricked or scratched area. Checks for allergy to airborne allergens, food, and penicillin.
Intradermal skin test: used if the skin prick test comes back negative or inconclusive. Small amounts of allergens are injected into the outer layer of your skin (the epidermis). Checks for allergy to airborne allergens, medications, and insect bites.
Patch test: drops of the allergen are placed on your skin which is then covered with a bandage. After 48 to 96 hours, the bandage is removed to check for signs of an allergic reaction. Checks for the causes of contact dermatitis.
Blood (IgE) test: a sample of your blood is taken and sent to the lab for analysis. Allergens are added to the sample of your blood and the levels of IgE (immunoglobulin E) are measured.
Challenge tests: usually performed in a hospital setting. Individuals with a suspected food allergy must ingest small amounts of the food and an allergist will observe to see if any allergic reaction occurs.
Asthma testing
If your respiratory specialist (or pulmonologist) suspects that you have asthma based on your medical history and physical examination, the following diagnostic tests will be conducted for a more accurate diagnosis:
Spirometry: checks how much air you can exhale and how fast you can exhale after a deep breath. This helps to identify if your airways are narrowed or restricted.
Peak flow testing: measures how quickly you can exhale. Lower peak flow readings are signs that your lungs may not be working as well as it should.
Bronchoprovocation testing: also known as the methacholine challenge, used to test how reactive your lungs are to certain triggers.
X-rays: chest x-rays may be used to check if there are other issues causing your symptoms.
Blood tests: may be used to check for possible infections.
Will allergic asthma go away?
Asthma is a chronic respiratory condition and there is no cure. The main goal for asthma treatment is maintaining good control of your condition by reducing or minimising exposure to triggers. Continuous management and monitoring by your respiratory specialist are important. In addition to reducing or minimising exposure to triggers, asthma can be treated with the following medications:
Bronchodilators: help to relax the muscles around your airways, thereby preventing airway constriction.
Anti-inflammatory medications: help to reduce inflammation, swelling, and mucus production.
Anti-cholinergics: helps prevent your airway muscles from tightening
Biologics: these target specific antibodies in your body to prevent asthma-causing inflammation.
Allergies can be treated in the following ways:
Avoidance: limit or completely restrict exposure to the allergen.
Medication: certain medications work to reduce the response of your immune system thus easing symptoms.
Immunotherapy: also known as allergy shots, these are injections containing small doses of the allergens which are injected into your body, slowly training your immune system to recognise them as friend rather than foe.
Anti-IgE therapy: medications that interfere with the production of IgE and hence prevents an allergic reaction.
Anitha Jeyagurunathan, E. A. (2021). Asthma Prevalence and its Risk Factors Among a Multi-Ethnic Adult Population. Yale Journal of Biology and Medicine, 417-427.
