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Shellfish a common cause of food allergy here

  Thursday, 26 l 05 l 2011  Source: Mind Your Body; The Straits Times   
By: Lea Wee

The most common cause of food allergies in teenagers here is shellfish – mostly shrimp and crab. Shellfish allergy affects as many as five out of every 100 teenagers, according to a study by the National University Hospital (NUH). In comparison, fewer than one out of every 100 teenagers here has a peanut allergy. The researchers suspect the unexpectedly high rate of shellfish allergy is connected to the high rate of allergy to dust mites here.

Senior consultant paediatrician Lynette Shek, who authored the study, said: “Shellfish and dust mites share the same protein, tropomyosin. Hence, a person who is allergic to this protein in dust mites may also develop a hypersensitivity to the same protein found in shellfish.” She plans to embark on another study to test this theory. Dust mites are common in hot humid climates.

Said to be the largest study on food allergy in South-east Asia, the NUH study polled more than 23,000 local and expatriate children in Singapore and the Philippines aged between four and six, and between 14 and 16. The older children have a higher incidence of shellfish allergy (about 5 per cent) compared to the younger ones (about 1 per cent).

The group embarked on the study on shellfish, peanut and tree nut allergies to see if the trends in the two Asian countries would mirror those in the West. These allergies tend to last through life, unlike say, egg, cow’s milk or soya bean allergies, which children often outgrow. Prof Shek said: “There has been a substantial increase in peanut and tree nut allergies in the West over the last two decades. But we had the impression these are not as common in the East.”

The children completed a structured questionnaire between August 2007 and February 2008. The findings confirmed the researchers’ beliefs –with one exception. Expatriate children, whether Asian or white, who were born in the West, had a higher rate of peanut or tree nut allergy (about 1.2 per cent), compared to children in Singapore and the Philippines (0.5 per cent). The figure for expatriate children was closer to those of countries in the Western hemisphere.

Another study author, Dr Lee Bee Wah, a consultant paediatrician at Mount Elizabeth Medical Centre, said: “This suggests that the kind of food allergy a child develops may depend on the environment he is born into, including the food he is exposed to in his early years.” There is some speculation that children born in the West are more likely to develop a peanut allergy as previous guidelines encouraged mothers to avoid peanuts during pregnancy and breastfeeding and to delay introducing them to their infants.

Although peanut allergy is still uncommon here, another study by Dr Liew Woei Kang, a visiting consultant paediatrician at KK Women’s and Children’s Hospital (KKH), found it had overtaken bird’s nest as the top cause of food-induced anaphylaxis at KKH. Between 2005 and last year, severe allergic reactions to peanuts made up 14 out of 73 cases of food-induced anaphylactic shock. Shellfish and bird’s nest each accounted for nine cases.

The NUH study, published last year in the American Journal Of Allergy And Clinical Immunology, confirmed what other studies have found: the kind of food allergy a person develops may depend on his ethnicity. The risk of tree nut allergy in Indians here and the risk of peanut allergy in Malays here is four times higher than that of ethnic Chinese. Malays and Indians also have a higher incidence of other allergic conditions such as asthma, said Dr Lee. It is not known why this is so, she said, but this much is known: “Having an allergic condition predisposes people to developing a food allergy.”

Madam Farah Dilah, 36, a housewife, found out that her two-year-old daughter, Nur Iffah Nasarudin, was allergic to shellfish and eggs last year. The girl was diagnosed with eczema and given a skin prick test for other allergies. She said: “It was lucky we found out before we exposed her to any of those foods. She could have had a severe attack.”


If your child has a food allergy...

  1. Read food labels for ingredients. If in doubt, do not let your child eat the food.
  2. Learn the alternative names for the allergen. For example, peanut oil is also known as arachis oil and can be found in salad dressings and even dog food. Get to know scientific names such as casein and whey, which stand for cow’s milk, and ovalbumin for chicken egg.
  3. Teach your child to read food labels when he is old enough so that he will learn to look out for the allergens himself.
  4. Ask what the ingredients are when dining out.
  5. Get the help of your doctor to create an emergency plan. This can act as a guide to the use of emergency medicines like antihistamines and an adrenaline auto-injector such as an Epipen in an emergency. The plan should include information on the hospital closest to home and school as well as the role of family members, school teachers and all carers in an emergency.
  6. Let your child wear a medical alert card, bracelet or pendant when he eats out alone. If he has an allergic reaction and is unable to speak, people will know he has a food allergy.
  7. Carry an Epipen if it has been prescribed.

    Source: Dr Liew Woei Kang, a visiting consultant paediatric allergist and immunologist at Mount Elizabeth Hospital For more information on where to go for egg, dairy or nut-free food in Singapore or how to make these dishes yourself, visit The website was set up by two expatriate mothers here.
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