Every parent gets nervous about their baby developing a food allergy, and that’s totally understandable. It’s recommended that babies are introduced to allergens during weaning, so they’ll be less likely to develop an allergy. Vhi consultant paediatrician, Dr Caroline Lhopital, explains why this is the case, the types of food allergies, and tips for introducing allergens to your baby’s diet. 

Weaning is when we start introducing babies to solid food. It should start between four and a half to six months. This is the case whether you’ve been breastfeeding or formula feeding your baby. It’s a fun, messy and exciting time for both parents and babies! 

Common food allergies in babies

It’s important to say that babies aren’t born with food allergies. Allergies develop after birth and are more likely to occur in certain circumstances. A food allergy is your body's immune system reacting incorrectly to specific proteins that are found in foods. Your immune system sees the food as a threat and responds with the symptoms associated with an allergic reaction.

This is more likely to happen in children with immune conditions or a family history of allergies (asthma, eczema, hay fever…), or with eczema themselves, especially if the food is introduced late into their diet. That being said, anybody can develop a food allergy, at any age.

The most common food allergies we see in babies are egg, milk, soya, wheat, and nuts. Fish and sesame allergies tend to develop in older children. 

The two types of food allergies

There are two types of food allergies, and each one causes different symptoms. Allergies differ from intolerances or sensitivities in that each and every time your baby has the food that they are allergic to, the same symptoms will occur. If a food sometimes causes symptoms, but not consistently, it is unlikely that this is an allergy.

Immediate food allergy

This is an allergy that’s driven by a specific antibody (an antibody is a protein that your immune system produces to get rid of unwanted things from your body like bacteria and viruses) called IgE.

• With an immediate food allergy, you’ll usually see symptoms within a few minutes up to two hours of your baby eating the triggering food. Symptoms can include rash, swelling of the skin and lips, vomiting, diarrhoea, and sometimes there can be difficulty breathing, pallor or fainting.
• Most reactions are mild and will resolve spontaneously, but if your baby is reacting severely or struggling to breathe, call emergency services straight away for assistance.
• If you think your baby had an immediate food allergy, stop giving them the food they were eating and reach out to your healthcare provider for guidance. Generally, your baby will be referred for an evaluation and this might include skin-prick or blood testing.
• When the immediate allergy is confirmed, treatment includes avoiding the responsible food, antihistamines, and sometimes adrenalin (given through an adrenalin pen), especially if their reaction was severe to begin with. Your healthcare provider will explain how and when to use those.

Delayed food allergy

• This type of allergy is not driven by an antibody, and it takes between two to twenty-four hours for symptoms to develop. It can affect the skin, the gut or the airway system.
• The symptoms can include poor growth, tummy pain, vomiting, diarrhoea, blood in the stools, irritability and sometimes chestiness. This type of allergy is common in babies that are allergic to cow’s milk, for example.
• Since there are no antibodies involved, there are no blood or skin tests available to diagnose a delayed food allergy; instead, your healthcare provider will evaluate your baby and suggest an elimination diet (such as eliminating dairy if they feel dairy could be the culprit), to see if the symptoms stop. It’s recommended you try this elimination diet for four to six weeks before re-introducing the food to see if the symptoms come back again.
• The symptoms of a delayed food allergy are very similar to those of lots of other conditions, so be sure to chat to your healthcare provider before you decide to stop a food altogether.

Some babies can present with mixed-type allergy, where they would have mild immediate symptoms (a transient rash for example) followed by delayed allergy symptoms later on.

Note: The Vhi paediatric clinic treats delayed food allergic reactions only. Please contact your GP for mild immediate allergic reactions, and emergency services if your baby is having a severe immediate allergic reaction.

The importance of introducing allergens to your baby’s diet

It’s safe and recommended to introduce allergens to your baby’s diet pretty much as soon they have started weaning. Between four and six months of age is when the immune system expects lots of new proteins to come through the digestive system, and those new proteins will be learned and tagged as ‘harmless’ ─ we say the baby is becoming tolerant of the food. When their body is tolerant of a food, it won’t produce antibodies to fight against it (like it would a bacteria or virus), causing an allergic reaction.

On the contrary, if a new protein is presented after that ‘window of opportunity’, or through a different path than the digestive system (on the skin for example), it is more likely that the immune system will mark it as a threat and develop an allergy to it.

That’s why, it’s now recommended you don’t delay introducing allergenic food (such as nuts, dairy, wheat, or eggs) into your baby’s diet. This is especially important if your baby has eczema, or if there is a history of allergies in your family.

Tips and tricks for introducing allergens to your baby’s diet

It’s best for your baby to introduce all the allergens as you’re weaning them. There’s no need to hold off doing so unless your healthcare provider recommends it. Here are some tips and guidelines:

• Introduce the foods one-by-one. Don’t introduce more than one allergen at a time. This way, you’ll know for sure what causes a reaction if your baby has one. 
• Do it early in the day, so you can observe your baby for the next few hours, and on a day when you or someone who knows your baby well is present, so that any abnormal signs or change in their behaviour will be noticed.
• Do it on a day they are not sick (or it might be difficult to tell if a rash or vomiting was due to the new food or a bug)
• Start with a small quantity, such as half a spoon of allergen, directly in their mouth or mixed with a food they already tolerate.
• When your baby has eaten a new allergen, keep watch over them for the next two hours to check if there are symptoms of an immediate allergic reaction. If there is no sign of an immediate allergic reaction, continue to give your baby that new allergen about three times a week, slowly increasing the quantity to help their immune system develop a tolerance, then move onto another allergen the following week.
• Once they are okay with a food you can start mixing it up with others.

What is the recommended order for introducing allergens to a baby?

There is no recommended order for introducing allergens, but it’s best to first introduce the foods they are more likely to meet in their environment. You could start with dairy, then hard boiled eggs (mashed up) and then smooth nut butters, soya or wheat. An easy way to introduce dairy is to add milk or yoghurt to the purées you make. If your baby is already taking formula, they already are tolerant to dairy.

For nut butters, I recommend adding some hot water to loosen it, then add it to their porridge or just spoon-feed them a couple of portions. Never give whole or chopped nuts, but you can crush them up instead and then sprinkle this powder onto your baby’s food. Buy specific types of nuts individually and try them one-by-one, rather than buying mixed bags, to know for sure which nut your baby is reacting or tolerant to.

If your family is not commonly eating certain allergenic foods (such as dairy and eggs for vegan families, or peanut butter when someone else is already allergic in the family) it is still a good idea to introduce them early in your baby’s diet to prevent them from developing allergies. Once they are safely introduced, they should still be offered occasionally to keep that tolerance going.

• When giving your baby any of the allergens for the first couple of times, give them the food directly off a spoon. Don’t give them the spoon or the food to feed themselves. This is to make sure that the new food goes into their system through their mouth rather than through their skin. Applying a barrier cream or ointment around their mouth before giving them food is also a useful tip. It also helps as some acidic foods such as raw tomatoes or strawberries can cause an irritation around the mouth that could be mistaken for an allergic reaction.
• If your baby doesn’t like an allergen food the first time they try it, don’t force them. But try again every couple of days until they get used to it. You can also find ways to disguise the allergen, such as mashed potato mixed with some milk or feeding them products that have milk in it, like cheese. Just avoid mixing more than one new allergen together at a time. 

As I said previously, most food allergies in babies are limited to a face and body rash with some digestive signs like vomiting. If your baby has an immediate allergic reaction to an allergen, stop giving them the food, wash their face and hands and contact your healthcare provider for guidance.

Signs of a severe allergic reaction

In very rare cases, the allergic reaction can be severe and impact their breathing or circulatory system (this is called anaphylaxis). If you observe any of those signs following a new food:

• swelling of their throat and tongue
• difficulty breathing or breathing very fast
• difficulty swallowing
• hoarse cry or loss of voice
• wheezing, coughing or noisy breathing
• pallor (atypical paleness) or fainting

Don’t wait to call an ambulance, do it straight way. They will guide you through the next steps.

It’s natural to feel nervous about introducing allergens to your baby’s diet, but it’s the safe and recommended thing to do, so you can rest assured. Most often, introducing allergens is just like introducing other foods, and once it’s done you can be safe in the knowledge that your child can eat anything.

If you’d like more details on weaning, read my blog, ‘Is your baby ready for weaning? Signs and considerations.’ Your healthcare provider is always on hand to answer any questions or concerns you have along the way as you help strengthen your baby’s immune system with weaning. 

Useful links for parents:

Irish Food Allergy Network: https://www.ifan.ie/

Children’s Health Ireland: https://www.childrenshealthireland.ie/list-of-services/allergy/

This content is for information purposes only and is not intended or implied to be a substitute for professional medical advice, diagnosis, or treatment. Always seek advice from your GP or an appropriate medical professional if you have concerns about your health, or before commencing a new healthcare regime. If you believe that you are experiencing a medical emergency call 999 / 112 or seek emergency assistance immediately.

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