Food Allergies in Children: Symptoms, Triggers, and What to Do

As parents, we do our best to provide our children with the best nutrition, offering a wide range of foods for variety and balance. However, there are times when children develop reactions after eating certain types of food – a result of food allergies or intolerances.

What is a food allergy?

A food allergy is an abnormal response of the body's immune system to food. The immune system normally works to protect us against harmful microbes. When the immune system is triggered by food instead, a food allergy develops.

What causes a food allergy?

Some foods are more likely to trigger an allergic reaction in children than others, including eggs, milk, peanuts, tree nuts, soy and wheat.

Genetic predisposition is the most common reason why some children develop a food allergy: if either or both parents have food allergies, respiratory allergies or eczema, the child has an increased risk of developing a similar allergic condition.

Children with eczema also have a higher risk of developing food allergies.

Common food allergens in children

Almost any food can cause an allergy, but the following are among the most common triggers:

Cow's milk

An allergy to cow's milk is one of the most common childhood food allergies. Most children eventually outgrow it by the time they are 3–5 years old.

Eggs

Egg allergy is caused by an allergic reaction to the protein found mostly in egg whites. As it is impossible to eat egg yolk without traces of egg white, children allergic to egg protein need to avoid eggs altogether.

Soy

A soy allergy is often identified when an infant needs to switch to a soy-based formula after a suspected cow's milk allergy. Most children outgrow their soy allergy, though some remain allergic into adulthood.

Wheat and gluten

A wheat allergy may appear when a baby is introduced to wheat-based cereal during the transition to solid food. Bread and pasta are other common triggers. Some children react specifically to gluten, a protein found in wheat and certain other grains.

Seafood

Shellfish is one of the most common food allergens among older Asian children. Fish allergy is less common but can still occur.

Peanuts

Although peanut allergy is more prevalent in the West, it is one of the most common causes of severe allergic reactions in Singaporean children.

Tree nuts

Tree nuts include walnuts, pecans, cashews, Brazil nuts, almonds and hazelnuts. A person may be allergic to all tree nuts or only to specific types.

Symptoms of food allergies in children

The most common symptoms of a food allergy are skin-related. Within minutes to a few hours of eating the trigger food, a child may develop hives – red, itchy, raised rashes that vary in size and can appear anywhere on the body. Some children also develop swelling around the lips or eyes.

The second most common symptoms are gastrointestinal, including stomach pain, vomiting or diarrhoea.

In more severe cases, food allergies can cause breathing difficulties, swelling of the throat or tongue, or a drop in blood pressure that may cause the child to appear pale or feel faint.

Food intolerance vs food allergy: what is the difference?

Food intolerance is the body's inability to process food due to physiological reasons, not an immune response. The most common type is lactose intolerance, where the body lacks the enzyme lactase needed to break down lactose – the main carbohydrate in dairy products such as milk and cheese. Symptoms include abdominal pain, bloating and diarrhoea after consuming dairy.

Food intolerance can also be triggered by naturally occurring chemicals in food – such as caffeine – or by additives like monosodium glutamate (MSG), which may cause headaches, hot flushes or chest pain.

The key differences between food allergies and food intolerance are:

• Age of onset: food allergies are more commonly seen in infants and young children, while food intolerances tend to develop towards adolescence or adulthood.
• Dose threshold: children with a food allergy can react to even a tiny amount of trigger food. Food intolerance symptoms are dose-related – people are more likely to react when consuming a large amount or eating the food frequently.
• Severity: food allergies can result in anaphylaxis – a serious, potentially life-threatening reaction involving breathing difficulties, loss of consciousness and a drop in blood pressure. Anaphylaxis does not occur in food intolerance.

How are food allergies in children diagnosed?

When you bring your child for consultation, the paediatrician will ask detailed questions about your child's medical history, the foods that trigger a reaction, the symptoms that develop, and how quickly symptoms appear after eating.

Depending on your child's history, an allergist may perform one or more of the following tests to confirm the diagnosis:

• Skin prick test
• IgE (immunoglobulin E) blood test – to detect allergen antibodies formed in the presence of allergies
• Oral food challenge

What is a skin prick test?

A skin prick test is used to identify allergy-causing substances (allergens). Small amounts of suspected allergens are introduced into the skin and observed for a reaction. When an allergen enters the skin, the body produces antibodies to fight it; these antibodies trigger the release of chemicals such as histamine, producing an allergic reaction at the prick site.

How is a skin prick test done?

Before the test, your doctor will review your child's medical history and perform a physical examination. A small drop of the suspected allergen is placed on the skin of the child's back or forearm, and the surface is lightly scratched with a small needle. The skin is then observed for signs of an allergic reaction.

Results are available within 15 minutes. If your child is allergic to a tested substance, a red, swollen, itchy bump will appear at the prick site.

How to prepare for a skin prick test

Medications can interfere with results. Your child should not take any antihistamine medications or cough mixtures for 5 days before the test.

Is a skin prick test safe for children?

The skin prick test is safe and generally painless, though some children may find it slightly irritating. The skin reaction subsides on its own within a couple of hours. If the itch causes discomfort, oral antihistamine or a mild topical steroid cream may be prescribed.

The test can identify multiple allergens in a single session, helping your child's doctor develop a tailored allergy management plan.

How to manage food allergies in children

The primary approach to managing a food allergy is strict avoidance of the trigger food. This includes:

• Reading ingredient labels carefully on all packaged food products.
• Informing restaurant staff about your child's allergy and requesting that cooking equipment is not contaminated with the trigger food.
• Alerting key people in your child's life – childcare providers, school staff and parents of friends – about the allergy, how to recognise symptoms, and what to do in an emergency. A written action plan is helpful.

What to do during an allergic reaction

For mild symptoms (rashes, hives, watery or itchy eyes): over-the-counter antihistamines may be given as advised by a doctor or pharmacist. Watch closely for any changes and seek medical attention if symptoms worsen.

For severe symptoms (abdominal pain, nausea, vomiting, or difficulty breathing): administer an epinephrine injection immediately. Lay your child flat with their legs elevated and keep them warm. If they are vomiting or having trouble breathing, help them sit up or lie on their side. Take your child to the emergency department immediately, even if symptoms appear to improve.

If your child has been prescribed an epinephrine autoinjector, ensure they know how and when to use it, and that they carry it with them at all times.

When should you see a doctor?

Consult a doctor if you suspect your child has a food allergy. If your child develops severe symptoms – breathing difficulties, pallor or loss of consciousness – go to the nearest paediatric urgent care centre (UCC) without delay.

This article was reviewed by Dr Victoria Tan, paediatrician at Parkway East Paediatric Urgent Care Centre.