A food allergy is when the body's immune system reacts to specific proteins found in food.
Babies are not born with food allergies. Food allergies develop after birth. They are more likely to happen if you delay introducing foods such as dairy, egg and peanut to their diet.
Most food allergies affect children under the age of 3. Many children grow out of their food allergy by the time they start school.
Symptoms of food allergies
There are 2 main types of food allergies which cause different symptoms. These are immediate and delayed food allergies.
Immediate food allergy
An immediate food allergy can start within minutes or up to 2 hours after eating a certain food. This type of allergy usually happens the first time your child eats the food.
Symptoms include:
- a sudden rash
- lip and face swelling
There can sometimes be vomiting but it is rare this will happen without rash and swelling. Vomiting on its own is not usually a sign of an allergic reaction.
If you think that your child has had symptoms of a mild immediate allergic reaction, speak to your GP before giving them the food again.
Delayed food allergy
A delayed food allergy can take between 2 and 24 hours to show symptoms.
Symptoms of a delayed food allergy include:
- tummy (abdominal) symptoms
- vomiting
- diarrhoea
- blood in your child's poo
This type of allergy is more common in young babies and children who are allergic to cows' milk or cow's milk formula.
It is very rare in young babies and children with allergies to:
- peanuts
- tree nuts - such as almonds, brazil nuts, cashews, hazelnuts or walnuts
- fish
- shellfish
A severe allergic reaction that affects your child's breathing or blood circulation (anaphylaxis) is rare.
If your child has a delayed allergic reaction to cow's milk formula, do not change their formula yourself. Speak to your GP or public health nurse first.
There are special formulas available for babies with an allergy to cow's milk. Use these under medical supervision.
Do not use goats' milk or drinks labelled as almond, oat or rice milk.
Causes of food allergies
In children, the foods that most commonly cause an immediate allergic reaction are:
- egg
- cow's milk (including formula)
- peanut
Eczema is not a food allergy. But many children that had eczema as a baby will have a food allergy.
Diagnosing food allergies
Your GP will ask you some questions about your child's symptoms and their medical history.
If your GP thinks your child has a food allergy, they may:
- refer them to a paediatric or allergy clinic
- recommend that you reintroduce food that you have been avoiding while you wait for their allergy clinic visit
In most cases, your child might need to have an allergy test.
Most children with a milk and egg allergy can start graded programmes, such as the milk and egg ladders, before the test.
Preventing food allergies
If you're pregnant or breastfeeding, eat a healthy, varied and balanced diet.
Breastfeeding gives your baby the best start in life. If you can, breastfeed your baby while you wean them to solid foods that include common allergens like milk, egg and nuts. It may help lower their chances of developing a food allergy.
No milk formula can prevent your baby from developing a food allergy.
A family history of food allergies is not a major risk factor for your child developing a food allergy.
Do not remove a food or food group from your baby or child's diet unless they have a confirmed food allergy. Speak to your GP, public health nurse or a registered dietitian first.
Weaning
Give your baby solid foods as soon as they show signs that they are developmentally ready. This is usually when your baby is around 6 months, but not before 4 months.
Your baby is more likely to develop a common food allergy if you delay introducing foods such as dairy, egg and peanut to their diet.
If your baby has eczema, it is more important not to delay.
Starting your baby on solid foods (weaning)
How to introduce food allergens
Introduce your baby to all of the most common food allergens as soon as you start weaning.
Start with:
- dairy
- hard boiled egg
- peanut
Other allergens to introduce include:
- fish
- sesame
- tree nuts (almond, brazil, cashew, hazelnut, walnut)
- wheat
When you introduce dairy, egg, nuts or fish to your baby for the first time, start with at least a teaspoon of the food. Slowly aim to give them more until they eat a normal portion for their age.
Give your baby food directly off a spoon. Do not give your child the spoon or the food to feed themselves.
This is to make sure that the least amount of food as possible gets onto their skin. Especially if they have eczema on their hands or face.
Preparing the foods
You can make a puree with fruit, vegetables or cereal and add:
- milk or natural yogurt
- a mashed hard boiled egg
- a heaped teaspoon of smooth peanut butter or 3 to 4 crushed peanuts
- a smooth spread or blend of another type of nut
- mashed fish that has no bones
Give your baby each new food allergen around 3 times a week. This will help their immune system to develop a tolerance.
How to introduce tree nuts and peanuts to your child's diet (video)