Food allergy - the challenges keep coming. An interview with Dr Vicki McWilliam
It was the birthday dinner that went horribly wrong. In 2017 a British teenager with an allergy to dairy food ordered chicken at a London restaurant, unaware it was marinated in buttermilk - despite telling restaurant staff of his allergy. He died of a fatal allergic reaction soon after.
It’s a heartbreaking story that highlights one of the challenges that food allergy keeps throwing at parents and clinicians.
“In our clinic we’re now seeing more children with multiple food allergies and more children who don’t grow out of allergies, especially milk allergy, “ says Dr Vicki McWilliam, Allergy Dietitian with the Department of Allergy and Immunology at Melbourne’s Royal Children’s Hospital. “Once we’d have expected most children to grow out of their allergies to milk, wheat and eggs but many kids now have allergies persisting into later childhood and adolescence. This makes it harder for parents to manage shopping and avoid accidental exposure - the teenage years are a frightening time for parents because this is the age group with the greatest risk of reacting. “
What’s driving multiple allergies?
“Eczema is thought to play a role by predisposing children to food allergy if breaks in the skin expose them to food allergens. This is why there’s a focus on promoting skin protection in babies and young children - advising against soap and moisturisers with food-based ingredients like goat’s milk or oats, for instance, and recommending that parents don’t test foods by rubbing food on the skin,” says Vicki who combines clinical practice with research at the Centre for Food and Allergy Research at the Murdoch Children’s Research Institute. “We’re still waiting to find out if moisturising children’s skin makes a difference - the studies have been inconclusive so far.”
So many at risk kids - too few resources for testing
“Because skin prick testing or blood testing isn’t diagnostic of food allergy, the only way to truly determine if a child has a food allergy is to see what happens when they eat it - and in an ideal world, all children with a higher risk of food allergy (family history, eczema or other food allergies) would have a supervised oral food challenge in hospital, “she says.
“But waiting lists for major allergy centres are lengthy so we prioritise testing for milk and egg allergy because they’re nutritionally important in childhood. With other foods we tell parents to introduce individual nuts and other potentially allergenic foods in small amounts - such as one eighth of a teaspoon of nut butter. If there’s a reaction like mild hives or swelling then children are seen for an allergy review. ”
Parents are demanding oral immune therapy (OIT) - but it needs more research.
“Many Australian families are going to the US so their children can have this treatment. It’s done mostly with peanut allergy and involves getting children to eat minute amounts of the food they’re allergic to and building up the amount over time,” Vicki says. “It’s good at helping desensitise children so you raise the threshold at which a food is likely to cause anaphylaxis - but there are limitations.
“Many children need to maintain the food in their diet regularly. If there’s an interruption and the child can’t eat the food - if they have gastro, say - there’s a risk of the desensitisation wearing off. Another issue is many programs recommend that children avoid exercise for two hours after eating their treatment dose. This is why some clinicians argue that it’s better to just keep avoiding the food.
“A Lancet review of trials of OIT on peanut allergy this year found that although OIT could be desensitising, it increased allergic and anaphylactic reactions compared to avoiding the food.“
An alternative to OIT is a patch worn on the skin that delivers peanut protein. Compared to OIT, it results in a lower level of tolerance to peanut, but it still increases the tolerance threshold with less risk of anaphylaxis, she explains.
“The patch needs further research but many parents are angry that it’s not available - they feel Australian allergists are holding back for commercial reasons. But we want to be sure it’s safe and effective. “
Food allergy - growing or slowing?
The 2007 HealthNuts study of 5,300 infants by the Murdoch Children’s Research Institute reported that one in ten 12-month-olds in Melbourne had a food allergy. This study has now been repeated to see if food allergy prevalence in infants has changed (the EarlyNuts study). Results will be available early next year. But preliminary data suggests some good news: many parents are following the new allergy prevention guidelines to feed babies potentially allergenic foods earlier from around six months, Vicki McWilliam says.
“There’s been quite a shift - although with babies at high risk of food allergy, parents tend to be slower to introduce these foods.”