Food allergies in young children - what you need to know

Food allergies are important to identify as if left undiagnosed, they can sometimes result in serious allergic reactions. We asked leading consultant paediatrician and allergist Professor George Du Toit how to spot the signs of an allergy in children, what types of food allergy children grow out of, and which allergens need treatment.

How common are food allergies?

Food allergies are more common than you might think – they affect around 3 in 10 children, and are becoming more common. Hay fever is even more common in childhood affecting nearly a quarter of children, with symptoms coming on after the 3rd or 4th summer, and progressing into the teenage years. Hayfever may also lead to a milder, later onset, secondary form of food allergy known as the Pollen-Food Syndrome (previously called the Oral Allergy Syndrome). Whilst many children will wheeze during viral illnesses, persistent asthma is thankfully a less common condition in young children.

Children can be affected by a range of allergy conditions – including food allergy, eczema, hay fever, and asthma. Allergic conditions can interact with each other, for example, children with early-onset troubling eczema may go on to develop not only food allergy but also aero-allergies with symptoms of hay fever and asthma when older. There is a particularly close association between food allergy and eczema, and hay fever and asthma.

Food reactions will exacerbate eczema and paradoxically, uncontrolled eczema is the most common route of sensitisation and subsequent allergy to foods. It is therefore important to identify and treat eczema early, and to test for allergies with a plan for the early introduction of common food allergies to the diet. Similarly, patients with asthma will enjoy better control when their hay fever is well managed as the airway linings share a common immune system and response. Patients with uncontrolled asthma are at risk of more severe food induced allergic reactions.

How do I know what food my child is allergic to?

If your child has recurrently eaten and enjoyed a food, in age-appropriate portions, it is very unlikely they are allergic to that food.

Conversely, if your child dislikes or has an aversion of the food, and allergic symptoms are noted, within an hour of ingestion, this is very likely to be an allergy to that food, especially if the food in question is one of the more common food allergens such as egg, milk or peanut.

Certain symptoms clearly indicate an IgE-mediated allergy. For example, if your child or baby eats some peanut butter (in the absence of any other common food allergens) and develops immediate onset swelling, hives, vomiting, cough and wheezing, they are likely peanut allergic.

When your child goes to see an allergist they will take a detailed history of what your child has tried and what symptoms they have experienced. A single event of unequivocal symptoms, like the one described above, is strong evidence of an allergy. If it has happened on two or three occasions, the diagnosis is even more secure.

However, if your child hasn’t tried eating the food on its own, if the symptoms are more equivocal, or if there are other risk factors that could explain the testing, then the doctor would likely recommend testing:

• A skin prick test is where drop of the allergen is placed on the arm and a Lancet is used to lightly touch through this and to look for a hive that may result.
• A blood test can also be performed and this measures the IgE antibody: the allergy antibody

Both tests are accurate when the test results are highly positive or negative. It can be difficult to interpret tests that are low positive. Where a diagnosis is uncertain, we then rely on an oral supervised food challenge test. So here, we would provide increments of the food in a safe and supervised setting and look for symptoms. Of course, if an age appropriate amount of the food is eaten with no symptoms, that child is peanut tolerant.

Finally, it's important to be cautious of tests such as IgG4 tests. These are not accurate tests for food allergy.

Will my child outgrow their allergy?

It depends on what they are allergic to. For example, milk and eggs are considered childhood allergies as very few children will carry this into this second and third decades of life. Typically, after three, four or five years, they'll start eating baked milk and egg products, because the heating damages the allergen, and a year or two later they'll tolerate just regular milk and egg based products. Wheat allergy is also commonly outgrown as are soy and some other allergies.

Certain food allergies are less likely to be outgrown and are only outgrown in ten to fifteen percent of children. These include:

• fish allergy
• shellfish allergy
• peanut allergy
• tree nut allergies such as cashew and pistachio
• walnut allergy
• sesame allergy

Families often ask about active programmes to treat these allergies.

How is food allergy treated?

Most treatments consist of eating small incremental amounts of the food allergen, this is known as oral immunotherapy (OIT). OIT is complex and only to be undertaken in specialist clinics.

More products and treatment modalities are being trialled and are increasingly becoming available. Palforzia is the only approved product for the treatment of peanut allergy for children aged 4-17 years.