Greater tolerance of nuts means more peace of mind when eating out

SINGAPORE – Peanuts, cashews and pistachios. Five-year-old Alden Mingzhe Horn was so allergic to them that consuming a small amount could make him very ill.

He once broke out in hives after his father, who had eaten peanuts in the office, hugged him after work.

But instead of avoiding these foods, Alden’s parents have been including them in his diet as part of a relatively new treatment for food allergy known as oral immunotherapy (OIT). The aim is to build up his tolerance for a variety of nuts that he is allergic to.

The standard way to manage a food allergy is to identify the food in question and avoid eating it. But the treatment does exactly the opposite.

OIT introduces small amounts of the food the child is allergic to, with doses gradually increased over time. This increases the person’s threshold of reactivity – the minimum amount of food he must be exposed to, to trigger an allergic reaction – to the point that it becomes very difficult to get an allergic reaction, said Dr Soh Jian Yi, consultant at the division of paediatric allergy, immunology and rheumatology at the National University Hospital (NUH).

NUH’s allergy clinics see about 80 new cases of childhood food allergy every month. Alden is one of over 70 children who have enrolled in NUH’s food allergy immunotherapy programme since it was first implemented in 2015. About half of them have completed the treatment and the rest are ongoing.

The programme covers common allergenic foods such as peanut, cow’s milk, wheat, cashew and pistachio, of which peanut tends to be the most common food allergy in preschoolers – and the deadliest food allergy, said Dr Soh.

The team recently launched walnut OIT and plans to introduce other tree nuts such as hazelnut, almond and pecan into the programme.

The treatment comprises one to two sessions each month, during which the patient takes a dose of the allergen in the children’s day therapy ward under medical supervision. The patient is observed for two hours and discharged with sufficient doses to take daily, which will last them until the next visit where the dose is increased.

A course of treatment, which takes an average of five to 10 months, ranges from S$3,000 to S$6,000. The cost is halved for subsidised patients, said Dr Soh.

Peanut OIT is also available at some private paediatric allergy clinics.

The treatment is usually considered in older children with persistent food allergies, rather than younger children, as the latter may still outgrow their allergies naturally, said Dr Liew Woei Kang, consultant paediatrician at SBCC Baby and Child Clinic at Gleneagles Medical Centre, who offers the treatment in his practice.

As part of the consultation with parents who are considering the treatment for their child, there is a review of the child’s trend of allergy test results, reactions and likelihood of outgrowing the allergy in the next few years, said Dr Soh.

There is currently less experience doing food OIT in adults but positive results have been reported in centres worldwide, said Dr Liew.

The NUH’s programme is not available to adults, but Dr Soh said there are plans for local scientists to conduct research on shellfish OIT for adults.

Last month, a 27-year-old woman was hospitalised after she was served a dish containing shellfish, despite having informed restaurant staff of her allergy.

NOT A CURE, AND THRESHOLD MUST BE MAINTAINED

Although children who have completed the treatment can eat the foods they were treated for, they are not “cured” of the food allergy, said Dr Soh.

“If you have a post-treatment threshold of reactivity of 20 peanuts, eating 100 means you’ll still get an allergic reaction, although you won’t if you eat 10,” he said.

The person also has to take the food every week to maintain the threshold, or the effect wears off gradually after a few months, Dr Soh said. 

Studies suggest that food allergy is on the rise, mainly in the West. In Singapore, food allergy is estimated to affect 4 to 5 per cent of school-going children, said Dr Liew.

It is not known exactly what causes food allergies. Some theories include excessive hygiene, urbanisation, food processing, environmental pollution and increase in C-section rates, the deliberate delay of allergenic foods to young children and increase in skin eczema, say experts.

What is known, is that a severe allergic reaction can be dangerous or even fatal. Last year, NUH saw two cases of children who were hospitalised for severe allergic reaction, said Dr Soh.

Anecdotes of people with allergies suggest that awareness of food allergy in Singapore is relatively low.

“When I order food, I sometimes feel that people think I’m being picky. For a while, even my parents thought I was being a ‘crazy mum’ because I was so careful with Alden’s diet but they completely changed their view after they saw him suffering a bad allergic reaction from accidentally eating a berry granola bar containing cashew nut,” said Alden’s mother Lee Shiying, 36.

MIXED VIEWS ON THE TREATMENT

Attitudes towards OIT differ among medical professionals, however.

The treatment is presently not offered as a clinical service at KK Women’s and Children’s Hospital’s (KKH). “Given that there is insufficient evidence regarding the long-term safety and efficacy of OIT, most international guidelines do not recommend it as a standardised treatment in clinical practice,” said Dr Loh Wenyin, consultant at KKH’s allergy service, department of paediatrics.

While there is increasing evidence that OIT is effective in inducing de-sensitisation, it has not been as efficacious in inducing tolerance (being cured of the food allergy), said Dr Loh.

“Furthermore, it has been reported that the frequency of allergic reactions occurring in patients undergoing OIT is higher than in those avoiding the culprit food, even among those who might have been successfully de-sensitised, and some of these reactions can be life-threatening,” Dr Loh added.

Recent guidelines on offering the treatment clinically have emerged in Spain and the European Academy of Allergy and Clinical Immunology, said Dr Soh.

According to him, allergic reactions are common during the treatment and the frequency varies according to the protocol used. On average, a patient on NUH’s peanut OIT gets one reaction every 32 days or so, almost all of which are mild, said Dr Soh.  

Occasionally, moderate and severe reactions are possible and staff, patients and parents are given clear instructions on how to handle them in the day ward as well as at home.

“General lessons from studies, which we have translated into our OIT programme, is that careful patient selection, frequent smaller up-doses and longer intervals between up-doses all help to significantly improve the safety of OIT, and it can indeed be performed safely,” said Dr Soh.

Patients must be carefully selected and expectations must be realistic, he added. The patient and family must be committed to complying with the protocol and the clinical centres that offer it must have extensive experience.

Alden’s increased tolerance of nuts has made a difference to him and his family. He has completed the therapy for peanut, cashew and pistachio, and is starting on walnut OIT.

He now takes a total of 24 peanuts, 16 cashew nuts and 16 pistachio nuts each week as part of his maintenance dose, which exceed the amount he may encounter by accident.

Dining out has become less of a headache and his parents no longer avoid nuts in their diet.

“I didn’t eat my favourite foods like satay and popiah until six months ago,” said Mdm Lee.

Although the treatment is a “huge commitment” and requires much time and effort, his parents resolved to complete the programme.

“It’s easier for me to give him his maintenance dose twice a week than for me to manage a restaurant. It’ll be very hard for me to control his diet and the things he’s exposed to when he gets older,” said Mdm Lee.