Every day, paediatric allergists see children with all kinds of food allergies. These are reactions caused by eating a food the child is allergic to. They can develop mild reactions, such as a rash, or sometimes more severe reactions that cause breathlessness or dizziness, soon after eating the food.
Nowadays, more parents are talking about food allergy or writing about it on the Internet or asking their doctors about it. Also, studies suggest that food allergies are becoming more common in children in many parts of the world.
Strikingly, the prevalence and severity of these allergies mirror the degree of urbanisation and standards of living of people in those regions. City kids seem to be more prone to developing food allergies.
Peanut allergy, for instance, is common and much-feared in the United States and certain parts of Europe. Yet it is almost unheard of in many parts of rural Africa.
Years ago, expecting mothers were often told to avoid "allergenic foods" (a group of the eight major foods comprising milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat and soya bean; these foods account for about 90 per cent of all food allergies in the US).
It also used to be thought that those with eczema - a chronic itchy skin rash - should avoid allergenic foods as early as possible. (Children with eczema may be more at risk of developing allergies or asthma.) This was often done without checking for or confirming the suspected allergy. It was postulated that eating such foods led to the development of allergy.
More recent research has debunked this theory. Studies over the past decade have demonstrated consistently that avoiding foods of all types actually increases a baby's risk of allergy to that food, rather than lowering it.
Such preventive steps may be even more important for children with eczema, given the association between eczema and food allergy.
One concern is the time-dependency of these preventive measures, as a study published by Professor Gideon Lack's group in the New England Journal Of Medicine earlier this year demonstrated. Regularly eating peanuts (as peanut butter or a snack) prevents peanut allergy. But this preventive measure is effective only if a peanut allergy has not yet developed.
It seemed that the longer one waited to introduce peanuts to a baby, the higher the risk of him or her developing a peanut allergy. Though this study was only on peanut allergy and not other food allergies that appear early in life, this calls into question the wisdom of delaying the introduction of "allergenic foods" to a baby.
This has a few implications if we are to stem the rising tide of food allergies. Expecting mothers do not need to avoid allergenic foods. Also, do not deliberately delay introducing various foods to the baby when weaning him or her.
We may need to rethink our weaning practices, with allergenic foods being among the first foods to be introduced to a baby. This requires a change of mindset for parents as well as their doctors.
Once a person has developed a food allergy, however, the above measures no longer apply.
Food allergy is troublesome and standard care means avoiding the particular food. This can mean years of checking for it when going to parties, on school trips, shopping at the supermarket and so on, with all the attendant anxiety and burden for everyone in the family.
Furthermore, strict avoidance is often not possible; dairy products, egg and peanut are often hidden ingredients in many foods.
Current treatment for these food allergies is based on desensitisation, which involves giving the child precisely-measured amounts of the allergen frequently and in increasing doses to raise the threshold of reaction.
Simply put, where a child with peanut allergy might once have collapsed upon taking 1/10th of a roast peanut, such efforts would aim to make it possible for the child to take two, four or even 20 roast peanuts without any reaction.
Desensitisation is not a cure. In some children, once the process is over and they do not continue taking the allergen at least twice a week, the benefits disappear and they return to their former threshold of reaction.
It is not yet possible to predict who this will happen to. In older desensitisation studies, children would be expected to take the allergen at least twice a week for life.
Future studies aimed at improving the effectiveness of desensitisation may make it possible for children to take the allergen less often or, ideally, not at all and still be free of their allergies.
Surveys in the US showed a rise in the prevalence of food allergies in children under 18 years of age, to almost 4 per cent in 2007.
With the increasing prevalence of food allergies in the West, it was only natural that research aimed at treating these allergies arose there.
The first studies, in the early 1990s, involved injections of peanut extract through the skin. These were soon abandoned as the patients suffered frequent and severe side effects, likely related to the route of administration.
In the 2000s, the first published studies on desensitisation by eating certain foods began to show promising results.
Further research focused on altering the routes of desensitisation, and adding ingredientsto increase the effectiveness of this treatment. However, these developments were invariably very expensive, which made them inaccessible to most people.
Hence at the National University Hospital, we began planning our own research on food desensitisation, with the ultimate aim of translating it into feasible, routine clinical service.
In December 2013, the first children began desensitisation for their peanut allergy. This required them to eat precisely-measured amounts of peanut allergen on a daily basis, over more than a year.
As with any research in its infancy, even with safeguards and the benefit of lessons from our predecessors in the West, there were teething problems - missed doses, side effects, making the desensitisation fit the child and parents' schedule, to name a few.
In this, I have my wonderful patients to thank, for they and their families patiently weathered the side effects, most of them minor. The children benefited - all who reached the target desensitisation dose could take 14 to 28 roast peanuts without any allergic reaction.
With the lessons learnt, we modified the desensitisation to increase its safety and effectiveness. This was bolstered by a study done at the Royal Children's Hospital, Melbourne, which suggested that the addition of Lactobacillus rhamnosus (a probiotic) increased the effectiveness and safety of desensitisation.
We have begun providing this service to children with peanut allergy. We chose peanut because it is associated with more serious allergic reactions, so the benefits would be potentially greater.
Further research into desensitising children with egg and milk allergy has begun and, in years to come, we will see an expansion of the programme to include other foods, as well as exploring other avenues of simple, practical desensitisation.
Ultimately, though, prevention is better than treatment.
Research on effective prevention and treatment of food allergies is ongoing. Meanwhile, we can review our weaning practices.
- The National University Hospital is holding a free public forum on allergies and asthma in children tomorrow. Topics include travelling with an asthmatic child, will my child outgrow asthma and allergy developments. Those who want to register for the talk can e-mail: firstname.lastname@example.org, or call 6772-4420. The talk will be held at the auditorium at NUHS Tower Block, Level 1, 1E, Kent Ridge Road.