14 February 2019
- Dr. Thulja Trikamjee
Article on Allergies
What is an allergy?
An allergy occurs when your immune system is sensitive to, and therefore reacts on exposure to a foreign substance.
What is an allergen?
Absolutely anything can serve as a stimulus for an allergic reaction, but common culprits include foods, preservatives and chemicals, pollen, pet dander, bee venom, and drugs.
So, why the buzz?
The prevalence of asthma and allergic diseases are increasing worldwide, particularly in low and middle-income countries. Globally, 300 million people suffer from asthma and about 200 to 250 million people suffer from food allergies. One tenth of the population suffers from drug allergies, and 400 million from rhinitis.
The Centre for Disease Control & Prevention reported a 50% increase in food allergy in children between 1997 and 2011, and the prevalence of peanut allergy has more than tripled in the same time period. Childhood hospitalizations for food allergy tripled between the late 1990s and the mid 2000s, and atleast 40% of children with food allergy have experienced a severe reaction or anaphylaxis.
Worldwide, allergic rhinitis affects between 10% and 30% of the population. In 2012, 7.5% or 17.6 million adults, and 6.6 million children were newly diagnosed with hay fever related to environmental allergens.
Food Allergy Reactions are serious and can be life-threatening.
Every three minutes, a food allergy reaction sends someone to the emergency room. Each year in the U.S., 200 000 people require emergency medical care for allergic reactions.
What about South Africa?
Allergic disease affects one in five people in sub-Saharan Africa, and this places a significant burden on our medical costs, as well as quality of life. School absenteeism and failure has been strongly associated with allergic disease, and it is therefore an important symptom not to ignore.
How and Why do Allergies Develop?
Allergies are your body's reaction to allergens, a sign that your immune system is working overtime. The first time your body encounters an allergen, your plasma cells release IgE (immunoglobulin E), an antibody specific to that allergen. IgE attaches to the surface of your mast cells.
Mast cells are found in great numbers in your surface tissues (ie. those with proximity to the external environment, such as your skin and in the mucous membranes of your nose), where they help mediate inflammatory responses. Mast cells release a number of important chemical mediators, one of which is histamine.
So, the second time your body encounters a particular allergen, within a few minutes, your mast cells become activated and release a powerful cocktail of histamine, leukotrienes, and prostaglandins, which trigger the entire cascade of symptoms you associate with allergies: sneezy, runny nose, sore throat, hacking cough, itchy eyes, etc.
Histamine can also cause airways to constrict, like with asthma, or cause blood vessels to become more permeable, leading to fluid leakage or hives. Leukotrienes cause hypersecretion of mucus, which you commonly experience as a runny nose or increased phlegm.
What are the most common food allergies?
A group of the eight major allergenic foods comprises milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat and soybean. If you develop a symptom or reaction to any of these or otherwise undefined food, it is important to be tested in a unit with good knowledge of allergy diagnostics. A simple skin test or blood test can reveal whether or not you are sensitive or allergic to a food or substance.
Will I outgrow my allergies?
Yes, a larger percentage of children outgrow most of their food and chest allergies, and this is why it is important to follow up with an allergy trained medical professional to ascertain this. Blood levels can confirm if your allergy is increasing or decreasing, and patients who are outgrowing their allergy are subject to an oral food challenge. This procedure is performed in hospital by a trained doctor or nurse, and involves feeding a patient small amounts of the culprit food in a controlled environment, to confirm that the given food is tolerated with no reaction. These will now be performed at the Melomed Allergy Service via the medical wards.
There are currently only a handful of experienced clinicians offering expert Allergy Diagnosis and Management in the health care sector in our country. The last decade has seen an incredible surge in research and information in the Allergy/Immunology World, and keeping up to date with new strategies and international policies can alleviate significant morbidity and mortality.
Dr Thulja Trikamjee is a specialist Paediatrician, with a sub-specialty Certificate in Paediatric Allergy/Immunology, as well as a Diploma in Allergy. She is currently a consultant at the University of Cape Town Lung Institute, an active member of the Allergy Society of South Africa, and an elected board member of the European Academy of Allergy and Clinical Immunology.
Her interests include Asthma, Food Allergy, Allergic Rhinitis, Drug and latex Allergy, Atopic Dermatitis/Eczema, Immunotherapy, Immunodeficiency, Urticaria, Angioedema, Allergy diagnostics and testing. She will be consulting children and adults at the Melomed Tokai Hospital every Tuesday.