Wednesday, December 7

The forbidden food

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Common among children, food allergies can be better managed with these tips

Dr Chong Kok Wee

EGGS, cow’s milk, peanuts, shellfish, wheat, soy and fish — these common foods are found in many dishes and store-bought products. However, they are also the most common food allergens.

Every week, KK Women’s and Children’s Hospital (KKH) treats infants with allergic reactions after being introduced to eggs for the first time. Indeed, food allergies affect up to five per cent of children in Singapore and are usually diagnosed in early childhood before two years of age.

“A food allergy happens when the immune system mistakenly treats harmless proteins in certain foods as a threat,” said Dr Chong Kok Wee, Head and Consultant, Allergy Service, Department of Paediatrics, KKH.

In most cases, the body develops an immediate reaction when antibodies are activated and chemicals such as histamine are released. Most of these reactions tend to be mild to moderate, with symptoms such as itchy rashes known as hives, itch in the mouth, facial swelling, acute vomiting, abdominal pain, or diarrhoea.

KKH also sees an average of two to three cases of severe reactions each week, said Dr Chong. Known as anaphylaxis, this allergic reaction may cause narrowing of the airways, leading to wheezing and shortness of breath. It may also cause a drop in blood pressure, leading to unconsciousness. Anaphylaxis should be promptly treated with intramuscular adrenaline and the patient should be conveyed to a hospital for further monitoring.

Key factors

In general, infants with moderate to severe eczema are more likely to develop food allergies.

“The development of food allergies is likely the result of complex interplay between genetic and environmental factors in early life,” Dr Chong said.

The general shift to an urbanised lifestyle, for instance, is associated with development of food allergy. Improved hygiene may result in insufficient exposure to microbial, which is necessary to strengthen the gastrointestinal tract and immune function.

Another key factor is when and how common allergens are introduced. If common food allergens are introduced to a child’s diet early, this may reduce the risk of allergies to these foods. In fact, there is no need to delay the introduction of common allergens such as eggs or peanuts.

Also, a more proactive approach to introduce common allergens early may be justified in high-risk children (who have a history of egg allergy and/or severe eczema), as a means to prevent peanut allergy.

However, if common food allergens are introduced via the skin, such as product application, this may instead increase allergic sensitisation. This is known as the dual-allergen exposure hypothesis, which suggests that early exposure to food proteins absorbed by the skin through disrupted skin barriers (as seen in eczema) leads to allergic sensitisation to the food.

Contrastingly, early exposure to food proteins via the oral route induces tolerance by the immune system. Earlier studies had proven this association between the application of peanut oil on the skin and an increased risk of developing peanut allergy. Nowadays, there is also an increase in cases of coconut and oat allergies in children who had reported usage of emollients containing these food proteins in them.

Managing food allergies

Patients who suspect a food allergy should see a doctor, who will make a diagnosis based on the history of immediate allergic reaction to a specific food, as well as a skin prick test or allergen-specific immunoglobulin E test.

In difficult-to-diagnose cases, doctors may conduct a medically supervised feeding of the food under controlled settings in an allergy clinic, said Dr Chong. It is also important to note that there are several unvalidated allergy tests that can be found online. These are not only inaccurate, but may also lead to unnecessary food restrictions that will impact a child’s nutritional status, psychosocial and emotional well-being. Therefore, it is important that tests are done within a professional medical setting.

If a food allergy has been diagnosed, the best approach is to avoid the allergen altogether. Children who are allergic to nutritious food such as cow’s milk, egg and wheat will be advised by dietitians on how to ensure adequate nutrition and optimal growth.

In some cases, avoiding allergens can be tricky. “Many may not be aware of ‘hidden’ ingredients within store-bought products. For example, bread usually contains milk, wheat is found in soya sauce, and eggs are used in medications such as lysozymecontaining syrups,” said Dr Chong, adding that patients should read food labels carefully.

Dining out may also increase the risk of accidental exposure, since food sold in hawker centres, food courts and restaurants do not come with an ingredient list. “Patients should be careful of cross-contamination of food that are sold or prepared in areas containing the allergen, as well as in places where common utensils are used for serving, such as at buffet lines. They are also advised to clean the surfaces of tables and chairs thoroughly before use,” Dr Chong said.

For some patients, even inhalation of the food allergen may trigger a reaction like rashes and runny nose, though severe allergic reactions are rare. To manage food allergies safely, patients are taught to recognise and treat symptoms promptly with adrenaline auto-injectors, such as an EpiPen.

Food oral immunotherapy (OIT), in which the allergen is consumed in gradually increasing amounts under medical supervision, also shows potential for improving tolerance. Trials for OIT* are ongoing, including a ‘Pancake Oral Immunotherapy for Egg Allergy in Inducing Tolerance’ trial currently conducted by KKH for children aged two to 15.

While OIT is currently not part of the standard treatment options, the good news is that certain food allergies may resolve on their own. “Up to 80 per cent of children may outgrow allergies to egg and milk. Peanut or shellfish allergies, however, tend to persist into adulthood,” said Dr Chong.

*To find out more about this trial, visit www.kkh.com.sg/POET or email Poet.Study@kkh.com.sg.