By Dr Amir Hamzah
Consultant Paediatrician and Clinical Immunologist/Allergist (Adults and Paediatrics)
MBBS, MMed (Paeds), MRCP, DipRCPath (Immunology), AM
Pantai Hospital Kuala Lumpur (Bangsar)
What’s an allergy?
An allergy is a hypersensitivity reaction due to an inappropriate immune response towards harmless substances. Thus, in allergic diseases, an immunological mechanism is responsible for the symptoms of hypersensitivity reactions. There are other conditions which present hypersensitivity reactions but are not due to allergy as there is no immunological mechanism involved. It is, thus, important to differentiate between these two situations as treatment strategies may differ.
What are examples of allergens?
Examples of allergens may be grouped into food, inhalants, drugs and insect stings.
Common food allergens include cow’s milk, egg white, soybean, wheat, peanut, tree nuts (e.g., hazelnut), fish and shellfish. Inhalants may be from the outdoors (e.g., grass or tree pollen) or indoors (most commonly dust mites). Drugs such as antibiotics, as well as insect stings (e.g., bee, wasp) may also cause allergies.
How common are allergies in children?
Allergy now affects up to 50 per cent of the population in some parts of the world. Of these, 70 per cent will develop allergic diseases during childhood and adolescence. Hence, allergic diseases must be seen as a global public health issue, especially since the quality of life in children is easily compromised early in life. The prevalence of allergy is continually rising and prevention is important.
Eczema tends to be the earliest manifestation of allergy and may occur concurrently with food allergies, with clinical symptoms that tend to peak during infancy. At toddler age, these two presentations would start to decrease, but there is then a higher risk of developing respiratory allergies, i.e., asthma and allergic rhinitis. The progression of one type of allergy to another as the child grows older is known as allergy or atopic march.
How will I know if my child develop an allergy?
Allergic diseases have many presenting features that affect the skin, airways (nose and lungs), and gastrointestinal organs. Hives (urticaria), flushing, itchiness and soft tissue swelling (angioedema) may be acute presentations of allergy involving the skin. Meanwhile, blocked and runny nose, as well as itchy nose and sneezing is suggestive of allergic rhinitis. Up to 70 per cent of asthma in children is likely related to allergy, and the features of this allergy includes wheezing, nocturnal cough and difficulty in breathing. Abdominal pain, discomfort, bloating, as well as diarrhoea may also suggest allergy. A severe life-threatening allergic reaction is known as anaphylaxis and can lead to death if not immediately recognised and treated appropriately with adrenaline (epinephrine).
How can I figure out what my child is allergic to?
Once there is suspicion of an allergy following a detailed history of the symptoms and physical examinations, potential allergens can be tested via blood (specifically IgE and total IgE) and skin prick tests. These tests are valuable in helping the doctor diagnose the allergy and determine the most likely cause of the allergy. If food is suspected as a cause, it is then important to do an allergy test to determine if your suspicion is right. Avoiding foodstuff not responsible for the allergy may be detrimental to a child’s health.
How can I protect my child from allergens?
Avoiding allergens (once confirmed following proper tests) is the cornerstone of allergy management. Depending on the allergen, avoidance could entail simple elimination. This could range from eliminating a certain food from your child’s diet to reducing exposure to inhalants or aero-allergens such as dust mites by washing bedding materials including mattresses and pillow dust mite protectors weekly at 60°C, and the use of HEPA (high efficiency particulate air) filter in vacuum cleaners.
Are allergies inherited?
There is a tendency for allergies to occur in families, but it is not well defined whether there is a sole genetic cause resulting in allergies being heriditary. The exact cause of allergy is still unknown. More recent scientific studies reinforce the perceived idea that the environment, including nutrition and infections play an important role in an individual potentially developing an allergy. This concept is often referred to as epigenetic.
What can I do to prevent my child from allergy?
There are three types of prevention – primary, secondary and tertiary. In essence, tertiary prevention is simply the treatment of allergic diseases. For example, taking medication when one has symptoms or a disease flare-up to stop or prevent the symptoms from getting worse. Once the symptoms are under control, the next step would be to avoid the allergens responsible.
Secondary prevention aims at preventing one form of allergic disease from progressing from one form to another, e.g., from eczema to asthma (halting the allergy march) and/or preventing someone who is known to be sensitised to an allergen from developing symptoms. Hence, sensitisation to an allergen (as shown by a blood or skin prick test) does not mean one has an allergy at any particular stage, but may be at a higher risk of developing an allergic disease in the future.
In primary prevention of allergy, one hopes to prevent an individual from developing sensitisation to allergens. Various methods have been studied in the primary prevention of allergy including the use of hydrolysed milk, probiotics and prebiotics in high-risk infants. There have been varying results in the outcome on the success of primary prevention of allergy. Further strategies for a pregnant mother (especially with known allergies) include the supplemental use of polyunsaturated fatty acid and vitamin D, but more clinical research is required before confirming the benefits of using these agents.
Is there any medication to treat allergies in my child?
Medication is available for treatment of allergies, depending on the allergic symptoms. The main group of medication for allergic diseases is antihistamines and steroids prepared in various forms i.e., by mouth, nasal spray, inhalers and cream.
Can allergy be cured?
No, allergy cannot be cured till the cause is known. However, potential ‘cure’ in the form of long-lasting remission periods from allergic symptoms may occur with allergen-specific immunotherapy. Currently, patients with allergic diseases presenting as allergic rhinitis (with or without allergic conjunctivitis) due to inhalant allergens (e.g., pollens, dust mites, cat and dog dander) and insect stings (e.g., bee, wasp) can undergo immunotherapy. Immunotherapy for food allergy is still being researched, but early results have shown there is promise for a cure.