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Children who are severely allergic to milk may be able to start tolerating it if they are given tiny amounts of baked milk followed by progressively larger doses, a small clinical trial suggests. Larger studies are needed to confirm the effect and the therapy shouldn鈥檛 be attempted without medical supervision, doctors say.

About 3 per cent of preschool-aged children are allergic to proteins in cow鈥檚 milk, making it the most common food allergy in young children. Most naturally outgrow it by the time they go to school, but one in five of them continue to be allergic as they get older.

Children with persistent milk allergies and their parents have to be vigilant because milk can be hidden in unexpected products like crisps and breakfast cereals. Milk has now overtaken peanuts to become the most in schoolchildren in the UK.

at Johns Hopkins University in Baltimore, Maryland, and her colleagues tested whether children with a severe cow鈥檚 milk allergy 鈥� who react even to trace amounts of milk 鈥� could learn to tolerate it if they were gradually exposed to baked milk, which is typically less allergenic than raw milk.

The team randomly assigned 30 people aged between 3 and 18 with a severe cow鈥檚 milk allergy to either slowly have baked milk powder introduced to their diets or a placebo powder made of tapioca flour.

Each day, children ate a baked cupcake or muffin made with ingredients including some of the powder, starting with a dose of 0.1 milligrams and building up to 2 grams over the course of a year. They didn鈥檛 know whether they were consuming the baked milk or placebo powder.

At the end of the year, the children were tested with increasing doses of baked milk under clinical supervision. Eleven of the 15 who had been gradually exposed to baked milk were able to tolerate a cumulative dose of 4 grams of the powder, which is about half a cup of milk鈥檚 worth. None of the children in the placebo group were able to reach this dose.

Since then, the children who could tolerate baked milk have also been tested to see if they can tolerate uncooked cow鈥檚 milk. So far, they have all been able to manage some amount of uncooked milk, ranging from small to large amounts, says Dantzer, who will publish these follow-up results next year.

鈥淭hey鈥檝e really enjoyed not stressing as much about being exposed to traces of milk,鈥� she says. 鈥淚t means they can order food from restaurants and not have to worry that it might have been cooked on the same grill as a cheeseburger.鈥�

The most common symptoms experienced while introducing baked milk included itchy mouths and stomach pain. Of the 10,000 baked milk doses that were ingested in the trial, four resulted in reactions strong enough that they necessitated the use of an EpiPen. Because severe reactions like anaphylaxis can occur, this therapy should only be conducted under guidance from an allergy specialist, says Dantzer.

The reason why baking milk makes it easier to tolerate is because heating milk protein changes its structure and embedding it inside cake changes the way the immune system accesses it, says at Murdoch Children鈥檚 Research Institute in Melbourne, Australia. 鈥淕radual exposure allows the immune system to reprogram itself so instead of activating the allergic pathway, it switches towards accepting the protein is OK,鈥� she says.

McWilliam and her colleagues are about to a begin a trial investigating whether gradual baked milk exposure also helps to treat mild to moderate cow鈥檚 milk allergy in babies under the age of 1. 鈥淚ntroducing baked milk at this age may allow us to switch off cow鈥檚 milk allergy early in life,鈥� she says.