What are food allergies and how will you know if you have one?
Reporters: Elaine Ng, Katie Cheng, Selena Chan
Editor: Fiona Chan
Research shows that around 8 percent of children and 3 percent of adults in Hong Kong suffer from food allergies. Common allergies include reactions to eggs, milk, peanuts, nuts and shellfish.
Food allergies occur when our immune systems overreact to something that is normally harmless. In an allergic reaction, the immune system produces antibodies called Immunoglobulin E, or IgE. Immediate reactions appear within 10 to 15 minutes of exposure to an allergen and symptoms may include itching lips, a swollen face, or hives all over the body. In severe cases, they may cause a fatal response called anaphylaxis.
There are two reliable tests for food allergies offered by local hospitals and private laboratories, that is a skin-prick test and an allergen-specific IgE blood test. In the former, an allergen is applied to the surface of the skin and to observe whether there is any reaction, while in the latter, laboratory analysis is conducted to detect allergenic molecules in blood samples.
There is another test in the market, to measure an antibody called Immunoglobulin G, or IgG. Agnes Leung, a clinical lecturer from the Department of Paediatrics at the Chinese University of Hong Kong, advises against taking this test because it is not related to any specific allergic reaction and may produce misleading results. Instead she suggests those who be experience allergies to go for regular checkups to monitor their allergic reactions and see if there are any changes over time.
Leung urges parents of children who may have food allergies to watch out for the so-called Five D’s of food allergy, namely diet, dry skin, Vitamin D, dogs, and dirt, referring to a study by Murdoch Children’s Research Institute. Dogs and dirt are related to the ‘hygiene hypothesis’ which suggests that our immune systems need to be stimulated during development so that they can ‘learn’ how to attack potentially harmful things such as bacteria and viruses. Keeping everything spotlessly clean may not necessarily lead to a lower risk of allergy, says Leung.
Children with Vitamin D deficiency have also been found to be 10 times more likely to have food allergies. And those with dry skin or eczema have also been found more likely to suffer from food allergies.
Leung has noticed that some people will avoid giving their children many types of food even though they do not have food allergies. She discourages this and says children should be exposed to a wide variety of food as soon as possible to lower the risk of developing food allergies. Likewise, she says a mother-to-be should never refrain from consuming specific allergens during pregnancy unless she herself has food allergies.
As for those suffering from food allergies, there are always substitutes to the allergen. For instance those who are allergic to eggs can use silken tofu or mashed banana in their place in recipes, while soy milk, rice milk and almond milk are alternatives to cow’s milk.
However, Leung says there is little support for people with food allergies in Hong Kong. Most schools and restaurants in Hong Kong are not equipped with the EpiPen, an adrenaline injector for severe reactions. As for labelling and information, the Centre for Food Safety requires producers to state clearly if there are allergens on food labels. But there is no similar requirement for food items served in restaurants, and the presence of potential allergens is rarely indicated in menus. The lack of attention paid to food allergies is also reflected in the make-up of health personnel in the medical system. Leung says there is a lack of medical doctors specialising in allergic and autoimmune diseases.