Detecting food allergies

This story was first published in The Straits Times on Aug 1, 2013.

I'm avoiding giving eggs to my baby," said the mother of the cute eight-month-old baby sitting in my clinic.

"Why is that?" I asked.

"I've heard that eggs can cause allergy in babies."

I spent the next few minutes correcting that misperception and explaining why delaying the introduction of cooked eggs might be unwise.

The instinctive response, when someone has an allergy to something, is to avoid it.

Unfortunately, for many years, some had opined - in the absence of proof - that avoiding eating a food might prevent an allergy to it.

This advice included doing so to protect babies and young children. Parents were advised to delay introducing certain foods commonly associated with possibly causing allergies.

We then saw the rates of food allergy increase, rather than decrease, during this same period when "avoidance" was widely made known via the Internet.

In children, can food allergy be prevented?

Probably - but by eating the food.

Studies have shown that the earlier people are exposed to certain foods, the lower their risk of developing allergy to those foods.

How this works exactly is still not known. Some believe that early and regular ingestion of food will help prevent allergy.

Last year, an article in the Journal Of Allergy And Clinical Immunology: In Practice summarised the results of human studies so far.

There is no strong proof suggesting that avoiding or delaying the introduction of certain types of food to babies prevents allergy.

Rather, the risk of allergy is increased if the introduction of such foods is delayed.

Studies showed the risk of egg and wheat allergies to be higher if cooked egg and cereal were introduced after six months of age.

Other studies showed that if fish was introduced before nine months of age, the risk of fish allergy and eczema at one year of age was lower.

In essence, weaning foods should be introduced between four and six months of age and should not be deliberately delayed.

The exception to this rule is if a sibling has peanut allergy, in which case it may be safer to consult a doctor specialising in allergy first, before introducing that food.

And if a person already has an allergy to a food, then, yes, he should avoid it.

The question is, who has a real food allergy and who doesn't?


Recently, a patient from Indonesia came to see me. Her mother was worried that she had an egg allergy, because she would develop a rash if she ate eggs every day for a few days.

I asked a few more questions, examined the child, then told her mother that her daughter did not have an egg allergy and to carry on allowing eggs in her diet.

The mother wanted to know if there was a need for tests.

I said no. Though a test might reassure the mother, a physician's duty is to neither traumatise patients nor waste their money on unnecessary tests.

I explained that I knew her daughter did not have an egg allergy through a detailed clinical evaluation, sufficient knowledge and reasoning.

This is not to say that tests are never necessary when seeing patients. Had the picture been suggestive of an allergy in any way, I would certainly have ordered tests for the patient.

Thus reassured, the family returned to Indonesia.

One month later, I saw the girl again. "Thank you, doctor," the mother said. "I let her eat eggs freely and the rash never came back."

This is not a rare scenario in my clinic.

Many parents think that their child has a food allergy when their child has a rash. Often, the rash is not due to a food allergy.

There are a few common causes of rash in children. A short-lived rash may be a heat rash or due to a viral infection. Rashes that last a long time are often due to eczema.

Food allergy symptoms can range from mild to life-threatening, manifesting in many ways; swelling of the face, difficulty breathing, dizziness and the patient may even collapse.

However, other illnesses can also cause these symptoms.

Parents should consult a paediatrician to find out the cause of the symptoms. If the question of food allergy is an issue, consulting a paediatrician specialising in food allergy is useful.


At the beginning of this year, I saw the two younger brothers of a boy who had anaphylaxis, a life-threatening allergic reaction, to peanuts.

His mother did not dare to allow the boys to eat any peanuts or tree nuts and she had come to see me to find out if the two younger boys also had a nut allergy.

Her concerns were spot on - if a child has a peanut allergy, the risk of peanut allergy in his siblings is seven times higher.

It could have been potentially fatal to give the two younger boys peanuts.

I reviewed the two boys and did the tests for them. The negative skin tests meant it was 95 per cent likely that they did not have a peanut allergy. But there was still a 5 per cent chance of the test being wrong.

I could not take any chances with their lives, given the danger of peanut allergy. The two boys came back to the hospital, where I reviewed them again, then had them eat increasing doses of peanuts under close monitoring and with the necessary medication and equipment to treat an allergic reaction.

Happily, this was uneventful. They were not allergic to peanuts. They also tested negative for allergy to tree nuts. I told their mother that they could freely eat any nuts.

The look of relief on the faces of the family members - not only the boys and their mother, but also their grandmother - said more than words ever could.

To this day, the two boys are eating nuts without problems and they and their parents do not have to check the ingredient list of every processed food items they eat or worry about accidental exposure to nuts.

Their mother had done the right thing for them.

Dr Soh Jian Yi is an associate consultant at the division of paediatric allergy, immunology and rheumatology at the National University Hospital.

This story was first published in The Straits Times on Aug 1, 2013.To subscribe to The Straits Times, please go to